Imaging device, imaging module, electronic device, and imaging method

ABSTRACT

A thin lightweight imaging device is provided. A highly convenient imaging device is provided. The imaging unit includes an imaging unit, a memory, and an arithmetic circuit. The imaging unit includes a light-receiving device, a first light-emitting device, and a second light-emitting device. The first light-emitting device has a function of emitting light in a wavelength range that is different from a wavelength range of light emitted by the second light-emitting device. The imaging unit has a function of making the first light-emitting device emit light and acquiring first image data. The imaging unit has a function of making the second light-emitting device emit light and acquiring second image data. The memory has a function of retaining the first reference data and the second reference data. The arithmetic circuit has a function of correcting the first image data with the use of the first reference data retained in the memory and calculating first correction image data. The arithmetic circuit has a function of correcting the second image data with the use of the second reference data retained in the memory and calculating second correction image data. The arithmetic circuit has a function of combining the first correction image data and the second correction image data to generate synthesized image data. The light-receiving device includes a first pixel electrode, and the first light-emitting device includes a second pixel electrode on the same plane as the first pixel electrode.

TECHNICAL FIELD

One embodiment of the present invention relates to an imaging device, animaging module, an electronic device, and an imaging method.

Note that one embodiment of the present invention is not limited to theabove technical field. Examples of the technical field of one embodimentof the present invention include a semiconductor device, a displaydevice, a light-emitting apparatus, a power storage device, a memorydevice, an electronic device, a lighting device, an input device (e.g.,a touch sensor), an input/output device (e.g., a touch panel), a drivingmethod thereof, and a manufacturing method thereof. A semiconductordevice generally means a device that can function by utilizingsemiconductor characteristics.

BACKGROUND ART

A technique for forming a transistor by using an oxide semiconductorthin film formed over a substrate has attracted attention. For example,an imaging device with a structure in which a transistor that includesan oxide semiconductor and has an extremely low off-state current isused in a pixel circuit is disclosed in Patent Document 1.

REFERENCE Patent Document

[Patent Document 1] Japanese Published Patent Application No.2011-119711

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

An object of one embodiment of the present invention is to provide athin lightweight imaging device. An object of one embodiment of thepresent invention is to provide an imaging device capable of forming ahigh-resolution image by imaging. An object of one embodiment of thepresent invention is to provide an imaging device capable of forming ahigh-quality image by imaging. An object of one embodiment of thepresent invention is to provide a multifunctional imaging device. Anobject of one embodiment of the present invention is to provide a highlyconvenient imaging device. An object of one embodiment of the presentinvention is to provide an imaging device with high colorreproducibility. An object of one embodiment of the present invention isto provide a novel imaging device. An object of one embodiment of thepresent invention is to provide an imaging method with high colorreproducibility. An object of one embodiment of the present invention isto provide a novel imaging method.

Note that the description of these objects does not preclude theexistence of other objects. One embodiment of the present invention doesnot need to achieve all the objects. Other objects can be derived fromthe description of the specification, the drawings, and the claims.

Means for Solving the Problems

One embodiment of the present invention is an imaging device includingan imaging unit, a memory, and an arithmetic circuit. The imaging unitincludes a light-receiving device, a first light-emitting device, and asecond light-emitting device. The first light-emitting device has afunction of emitting light in a wavelength range that is different froma wavelength range of light emitted by the second light-emitting device.The imaging unit has a function of making the first light-emittingdevice emit light and acquiring first image data. The imaging unit has afunction of making the second light-emitting device emit light andacquiring second image data. The memory has a function of retaining thefirst reference data and the second reference data. The arithmeticcircuit has a function of correcting the first image data with the useof the first reference data retained in the memory and calculating firstcorrection image data. The arithmetic circuit has a function ofcorrecting the second image data with the use of the second referencedata retained in the memory and calculating second correction imagedata. The arithmetic circuit has a function of combining the firstcorrection image data and the second correction image data to generatesynthesized image data. The light-receiving device includes a firstpixel electrode, and the first light-emitting device includes a secondpixel electrode on the same plane as the first pixel electrode.

In the above imaging device, the light-receiving device further includesan active layer and a common electrode, and the first light-emittingdevice further includes a light-emitting layer and the common electrode.The active layer is positioned over the first pixel electrode andincludes a first organic compound. The light-emitting layer ispositioned over the second pixel electrode and includes a second organiccompound. The common electrode includes a portion overlapping with thefirst pixel electrode with the active layer therebetween and a portionoverlapping with the second pixel electrode with the light-emittinglayer therebetween.

In the above imaging device, the imaging unit preferably furtherincludes a lens. The lens includes a portion overlapping with thelight-receiving device and is positioned over the first pixel electrode.Light passing through the lens preferably enters the light-receivingdevice.

One embodiment of the present invention is an imaging module includingthe above imaging device and at least any one or more of the connectorand the integrated circuit.

One embodiment of the present invention is an electronic deviceincluding the above imaging module and at least any one or more of anantenna, a battery, a housing, a camera, a speaker, a microphone, and anoperation button.

One embodiment of the present invention is an imaging method including:the step of making a first light-emitting device emit light andacquiring first image data; the step of correcting the first image datawith the use of first reference data and calculating first correctionimage data;

the step of making a second light-emitting device emit light andacquiring second image data; the step of correcting the second imagedata with the use of second reference data and calculating secondcorrection image data; and the step of combining the first correctionimage data and the second correction image data and generatingsynthesized image data. The first light-emitting device has a functionof emitting light in a wavelength range that is different from awavelength range of light emitted by the second light-emitting device.

Effect of the Invention

According to one embodiment of the present invention, a thin lightweightimaging device can be provided. According to one embodiment of thepresent invention, an imaging device capable of forming ahigh-resolution image by imaging can be provided. According to oneembodiment of the present invention, an imaging device capable offorming a high-quality image by imaging can be provided. According toone embodiment of the present invention, a multifunctional imagingdevice can be provided. According to one embodiment of the presentinvention, a highly convenient imaging device can be provided. Accordingto one embodiment of the present invention, an imaging device with highcolor reproducibility can be provided. According to one embodiment ofthe present invention, a novel imaging device can be provided. Accordingto one embodiment of the present invention, an imaging method with highcolor reproducibility can be provided. According to one embodiment ofthe present invention, a novel imaging method can be provided.

Note that the description of these effects does not preclude theexistence of other effects. One embodiment of the present invention doesnot need to have all these effects. Other effects can be derived fromthe description of the specification, the drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing an example of an imaging device.

FIG. 2A to FIG. 2C are top views showing examples of a pixel.

FIG. 3A to FIG. 3D are cross-sectional views showing examples of animaging device.

FIG. 4 is a conceptual diagram showing an operation of an imagingdevice.

FIG. 5 is a flowchart showing an example of an operation of an imagingdevice.

FIG. 6A to FIG. 6C are cross-sectional views each showing an example ofan imaging device.

FIG. 7A to FIG. 7C are cross-sectional views each showing an example ofan imaging device.

FIG. 8A to FIG. 8C are cross-sectional views each showing an example ofan imaging device.

FIG. 9A to FIG. 9C are cross-sectional views each showing an example ofan imaging device.

FIG. 10A to FIG. 10C are cross-sectional views each showing an exampleof an imaging device.

FIG. 11 is a perspective view showing an example of an imaging device.

FIG. 12 is a cross-sectional view showing an example of an imagingdevice.

FIG. 13A and FIG. 13B are cross-sectional views each showing an exampleof an imaging device.

FIG. 14A to FIG. 14C are cross-sectional views each showing an exampleof an imaging device.

FIG. 15 is a cross-sectional view showing an example of an imagingdevice.

FIG. 16A and FIG. 16B are circuit diagrams each showing an example of apixel circuit.

FIG. 17A and FIG. 17B are diagrams showing an example of an electronicdevice.

FIG. 18A to FIG. 18D are diagrams showing examples of electronicdevices.

FIG. 19A to FIG. 19F are diagrams showing examples of electronicdevices.

MODE FOR CARRYING OUT THE INVENTION

Embodiments are described in detail with reference to the drawings. Notethat the present invention is not limited to the following description,and it will be readily appreciated by those skilled in the art thatmodes and details of the present invention can be modified in variousways without departing from the spirit and scope of the presentinvention. Thus, the present invention should not be construed as beinglimited to the description in the following embodiments.

Note that in structures of the present invention described below, thesame portions or portions having similar functions are denoted by thesame reference numerals in different drawings, and a description thereofis not repeated. Furthermore, the same hatch pattern is used for theportions having similar functions, and the portions are not especiallydenoted by reference numerals in some cases.

In addition, the position, size, range, or the like of each structureillustrated in drawings does not represent the actual position, size,range, or the like in some cases for easy understanding. Therefore, thedisclosed invention is not necessarily limited to the position, size,range, or the like disclosed in the drawings.

Note that the term “film” and the term “layer” can be interchanged witheach other depending on the case or circumstances. For example, the term“conductive layer” can be changed into the term “conductive film”. Asanother example, the term “insulating film” can be changed into the term“insulating layer”.

Embodiment 1

One embodiment of the present invention is an imaging device includingan imaging unit, a memory, and an arithmetic circuit. The imaging unitincludes a light-emitting device (also referred to as a light-emittingelement) and a light-receiving device (also referred to as alight-receiving element). Specifically, light-emitting devices andlight-receiving devices are arranged in a matrix in the imaging unit,and the light-emitting devices emit light and the light-receivingdevices receive light reflected from the subject. The memory has afunction of retaining reference data. The arithmetic circuit has afunction of correcting image data output from the light-receiving devicewith the use of the reference data and calculating correction imagedata. The imaging device of one embodiment of the present invention hasthe following functions: making light-emitting devices of differentcolors sequentially emit light for imaging; calculating correction imagedata by correcting each of image data obtained from images formed by theimaging with the light of the respective colors; and combining thecorrection image data to generate synthesized image data. The imagingdevice of one embodiment of the present invention can display asynthesized image on the imaging unit, on the basis of the synthesizedimage data.

The light-emitting device preferably emits light in the visible lightwavelength range. As the light-emitting device, an EL element such as anOLED (Organic Light-Emitting Diode) and a QLED (Quantum-dotLight-Emitting Diode) is preferably used. As a light-emitting substanceincluded in the EL element, a substance which emits fluorescent light (afluorescent material), a substance which emits phosphorescent light (aphosphorescent material), an inorganic compound (e.g., a quantum dotmaterial), a substance which exhibits thermally activated delayedfluorescence (a thermally activated delayed fluorescent (TADF)material), and the like can be given. An LED such as a micro-LED (LightEmitting Diode) can be used as the light-emitting device.

The light-receiving device preferably has sensitivity in the visiblelight wavelength range. In particular, a light-receiving device havingsensitivity in the whole visible light wavelength range is preferablyused. As the light-receiving device, a PN photodiode or a PIN photodiodecan be used, for example. The light-receiving device functions as aphotoelectric conversion element that senses light incident on thelight-receiving device and generates charge. The amount of generatedelectric charge depends on the amount of light entering thelight-receiving device.

It is particularly preferable to use an organic photodiode including alayer containing an organic compound as the light-receiving device. Anorganic photodiode, which is easily made thin, lightweight, and large inarea and has a high degree of freedom for shape and design, can be usedin a variety of imaging devices.

In one embodiment of the present invention, an organic EL element ispreferably used as the light-emitting device, and an organic photodiodeis used as the light-receiving device. The structure of the organicphotodiode can have many layers shared with the organic EL elements.Accordingly, the light-emitting device and light-receiving device can beincorporated in the imaging device without a significant increase in thenumber of manufacturing steps. For example, an active layer of alight-receiving device and a light-emitting layer of a light-emittingdevice are separately formed, and the other layers can be shared by thelight-emitting device and the light-receiving device. Accordingly, theimaging device can be thin and lightweight. Note that a layer shared bythe light-receiving device and the light-emitting device may havefunctions different in the light-receiving device and the light-emittingdevice. In this specification, the name of a component is based on itsfunction in the light-emitting device. For example, a hole-injectionlayer functions as a hole-injection layer in the light-emitting deviceand functions as a hole-transport layer in the light-receiving device.Similarly, an electron-injection layer functions as anelectron-injection layer in the light-emitting device and functions asan electron-transport layer in the light-receiving device.

As the light-emitting devices, a light-emitting device emitting light ina red wavelength range, a light-emitting device emitting light in agreen wavelength range, and a light-emitting device emitting light in ablue wavelength range can be used, for example. These light-emittingdevices are sequentially made to emit light and the light-receivingdevices sense the light reflected, which enables a color image of thesubject to be obtained. Thus, the imaging device of one embodiment ofthe present invention can be used as a color image scanner. In theimaging device of one embodiment of the present invention, image dataobtained from an image formed by imaging with light of each color iscorrected to calculate correction image data, and pieces of suchcorrection image data are combined, whereby a synthesized image data canbe generated. In other words, even when the light-receiving devices donot have a spectroscopy function, the imaging device can achieve highcolor reproducibility. By using a light-emitting device with high colorreproducibility, the imaging device can achieve higher colorreproducibility.

In this specification and the like, a blue wavelength range is greaterthan or equal to 400 nm and less than 490 nm, and blue light has atleast one emission spectrum peak in the wavelength range. A greenwavelength range of green is greater than or equal to 490 nm and lessthan 580 nm, and green light has at least one emission spectrum peak inthe wavelength range. A red wavelength range is greater than or equal to580 nm and less than or equal to 680 nm, and red light has at least oneemission spectrum peak in that wavelength range.

Since the imaging device of one embodiment of the present inventionemploys a light-receiving device having sensitivity in the whole visiblelight wavelength range, it is not necessary to independently provide ared-light-receiving device, a green-light-receiving device, and ablue-light-receiving device, which allows imaging for a high-resolutionimage. The imaging device of one embodiment of the present invention canalso have a function of displaying an image because light-emittingdevices are included, and thus the imaging device can be highlyconvenient and have several functions. For example, an image formed byimaging by the imaging unit is displayed on the imaging unit, wherebythe image formed by imaging can be checked immediately.

The imaging device of one embodiment of the present invention can beapplied to a display portion of an electronic device. For example, atelevision device, a personal computer, a monitor for a computer or thelike, digital signage, a mobile phone, a portable game machine, aportable information terminal, or the like can be used as the electronicdevice. When the imaging device of one embodiment of the presentinvention is applied to a display portion in an electronic device, thedisplay portion can have an imaging function. The user can performimaging by putting the imaging subject on the display portion in theelectronic device. The image formed by imaging is immediately displayedon the display portion, so that the user can also check the image; thus,the electronic device can be highly convenient. The imaging device ofone embodiment of the present invention can be applied to individualauthentication when the light-receiving device images biologicalinformation such as a fingerprint or a palm print. The imaging device ofone embodiment of the present invention can also be applied to a touchsensor when the positional information of a target object that touchesthe imaging unit is sensed.

The imaging device of one embodiment of the present invention isdescribed with reference to FIG. 1 to FIG. 15.

Structure Example 1 of Imaging Device

FIG. 1 is a block diagram illustrating an imaging device 10 of oneembodiment of the present invention. The imaging device 10 includes animaging unit 61, a driver circuit portion 62, a driver circuit portion63, a driver circuit portion 64, and a circuit portion 65.

The imaging unit 61 includes pixels 60 arranged in a matrix. The pixels60 each include a light-emitting device and a light-receiving device.The light-receiving device may be provided in all of the pixels 60 or insome of the pixels 60. In addition, one pixel 60 may include a pluralityof light-receiving devices.

The driver circuit portion 62 functions as a source line driver circuit(also referred to as a source driver). The driver circuit portion 63functions as a gate line driver circuit (also referred to as a gatedriver). The driver circuit portion 64 generates a signal for drivingthe light-receiving device included in the pixel 60 and outputting thesignal to the pixel 60. The circuit portion 65 has a function ofreceiving a signal output from the pixel 60 and outputting the signal asdata to the arithmetic circuit 71. The circuit portion 65 functions as areading circuit. The arithmetic circuit 71 has a function of receiving asignal output from the circuit portion 65 and performing an arithmeticoperation. The memory 73 has a function of storing a program executed bythe arithmetic circuit 71, data input to the arithmetic circuit 71, dataoutput from the arithmetic circuit 71, and the like.

As the arithmetic circuit 71, for example, a CPU (Central ProcessingUnit), a DSP (Digital Signal Processor), a GPU (Graphics ProcessingUnit), or the like can be used. A structure may be employed in which theabove is obtained with a PLD (Programmable Logic Device) such as an FPGA(Field Programmable Gate Array) or an FPAA (Field Programmable AnalogArray).

As the memory 73, a memory device including a nonvolatile memory elementcan be suitably used. As the memory 73, for example, a flash memory, anMRAM (Magnetroresistive Random Access Memory), a PRAM (Phase changeRAM), a ReRAM (Resistive RAM), an FeRAM (Ferroelectric RAM), or the likecan be used.

The driver circuit portion 62 is electrically connected to the pixel 60through a wiring 82. The driver circuit portion 63 is electricallyconnected to the pixel 60 through a wiring 83. The driver circuitportion 64 is electrically connected to the pixel 60 through a wiring84. The circuit portion 65 is electrically connected to the pixel 60through a wiring 85. The arithmetic circuit 71 is electrically connectedto the circuit portion 65 through a wiring 86. The memory 73 iselectrically connected to the arithmetic circuit 71 through a wiring 87.

Each of the pixels 60 preferably includes two or more subpixels. Thepixel 60 preferably includes a subpixel including the light-emittingdevice and a subpixel including the light-receiving device. FIG. 2Ashows an example of the pixel 60. FIG. 2A shows an example in which thepixel 60 includes four subpixels, a subpixel 60R, a subpixel 60G, asubpixel 60B, and a subpixel 60PD. For example, the subpixel 60Rincludes a light-emitting device 91R that emits light in a redwavelength range, the subpixel 60G includes a light-emitting device 91Gthat emits light in a green wavelength range, the subpixel 60B includesa light-emitting device 91B that emits light in a blue wavelength range,and the subpixel 60PD includes a light-receiving device 91PD.

Although, as the pixels 60, four subpixels are arranged in a matrix oftwo rows and two columns in the example in FIG. 2A, one embodiment ofthe present invention is not limited thereto. Four subpixels may bearranged in a row, as illustrated in FIG. 2B. In addition, there is noparticular limitation on the arrangement order of the subpixels.

Although the colors of light emitted by the subpixels are three, red(R), green (G), and blue (B) in the example in FIG. 2A and FIG. 2B, thecombination of the colors and the number of the colors are not limitedthereto. Four colors, red (R), green (G), blue (B), and white (W), orfour colors, red (R), green (G), blue (B), and yellow (Y) may bepossible. FIG. 2C shows an example in which the pixel 60 includes fivesubpixels, the subpixel 60R, the subpixel 60G, the subpixel 60B, asubpixel 60W, and the subpixel 60PD and the subpixel 60W includes alight-emitting device 91W which emits white light. Note that colorelements used for the subpixels are not limited to the above, and may becombined with cyan (C), magenta (M), or the like. Although the areas ofthe subpixels are equal to each other in the examples in FIG. 2A to FIG.2C, one embodiment of the present invention is not limited thereto. Theareas of the subpixels may be different from each other.

FIG. 3A to FIG. 3D each show a schematic cross-sectional view of theimaging unit 61.

The imaging unit 61 in FIG. 3A includes a substrate 51 and a substrate59 and includes a layer 53 and a layer 57 between the substrate 51 andthe substrate 59. The layer 57 includes a light-emitting device such asthe light-emitting device 91R, and the layer 53 includes thelight-receiving device 91PD.

The imaging unit 61 in FIG. 3B includes the substrate 51 and thesubstrate 59 and includes the layer 53, a layer 55, and the layer 57between the substrate 51 and the substrate 59. The layer 55 includes atransistor.

In the imaging unit 61, for example, red (R), green (G), and blue (B)light is emitted from the layer 57 including the light-emitting devicessuch as the light-emitting device 91R and light from the outside entersthe layer 53 including the light-receiving device 91PD. Note that inFIG. 3A and FIG. 3B, the light that is emitted from the layer 57 andthen enters the layer 53 is indicated by arrows.

The layer 55 including a transistor preferably includes a firsttransistor and a second transistor. The first transistor is electricallyconnected to the light-receiving device 91PD included in the layer 53.The second transistor is electrically connected to the light-emittingdevice such as the light-emitting device 91R included in the layer 57.

The imaging device of one embodiment of the present invention has afunction of imaging the subject that touches the imaging unit 61. Forexample, as illustrated in FIG. 3C, the light-emitting device includedin the layer 57 emits light, a subject 52 touching the imaging unit 61reflects the light, and the light-receiving device 91PD included in thelayer 53 receives the reflected light. Thus, the subject 52 over theimaging unit 61 can be imaged.

The imaging device of one embodiment of the present invention can alsoimage the subject 52 that does not touch the imaging unit 61, asillustrated in FIG. 3D. Also with the imaging unit 61 illustrated inFIG. 3A, the subject 52 that does not touch the imaging unit 61 can beimaged. Note that in FIG. 3C and FIG. 3D, the light that is emitted fromthe layer 57 and reflected by the subject 52 and enters the layer 53 isindicated by an arrow.

An operation of the imaging device is described with reference to FIG. 1and FIG. 4. FIG. 4 is a conceptual diagram illustrating the operation ofthe imaging device. Here, description is made with reference to anexample in which imaging is performed using the light-emitting devicesof three colors, the light-emitting device 91R that exhibits a redcolor, the light-emitting device 91G that exhibits a green color, andthe light-emitting device 91B that exhibits a blue color, which areillustrated in FIG. 2A and FIG. 2B.

In the imaging unit 61, the light-emitting device 91R that emits redlight is turned on, and a first image IM_(R) is formed by imaging usingthe light-receiving device 91PD. A signal from the light-receivingdevice 91PD in each pixel (hereinafter, referred to as first image dataR_(X)) is output to the arithmetic circuit 71 through the circuitportion 65. In the imaging unit 61, the light-emitting device 91G thatemits green light is also turned on, and a second image IM_(G) is formedby imaging using the light-receiving device 91PD. A signal from thelight-receiving device 91PD in each pixel (hereinafter, referred to assecond image data G_(X)) is output to the arithmetic circuit 71 throughthe circuit portion 65. In the imaging unit 61, the light-emittingdevice 91B that emits blue light is also turned on, and a third imageIM_(B) is formed by imaging using the light-receiving device 91PD. Asignal from the light-receiving device 91PD in each pixel (hereinafter,referred to as third image data B_(X)) is output to the arithmeticcircuit 71 through the circuit portion 65.

In the arithmetic circuit 71, the first image data R_(X), the secondimage data G_(X), and the third image data B_(X) are each corrected. Thearithmetic circuit 71 corrects the first image data R_(X) with use ofthe reference data and calculates first correction image data R_(LSB).The arithmetic circuit 71 corrects the second data G_(X) with use of thereference data and calculates second correction image data G_(LSB). Thearithmetic circuit 71 corrects the third image data B_(X) with use ofthe reference data and calculates third correction image data B_(LSB).

Here, the reference data is described. As the reference data, blackreference data and white reference data are acquired in advance.

A subject serving for a black reference is imaged with red light, greenlight, and blue light, and first black reference data R_(min), secondblack reference data G_(min), and third black reference data B_(min) areacquired as the black reference data. The first black reference dataR_(min), is an output value output from the light-receiving device ofeach pixel in imaging with red light. The second black reference dataG_(min) is an output value output from the light-receiving device ofeach pixel in imaging with green light. The third black reference dataB_(min) is an output value output from the light-receiving device ofeach pixel in imaging with blue light. As the first black reference dataR_(min), the second black reference data G_(min), and the third blackreference data Bruin, for example, voltage values can be used. The blacksubject used to acquire the reference data preferably has an extremelylow reflectance.

In a similar manner, a subject serving for a white reference is imagedwith red light, green light, and blue light, and first white referencedata R_(max), second white reference data G_(max), and third whitereference data B_(max) are acquired as the white reference data. Thefirst white reference data R_(max) is an output value output from thelight-receiving device of each pixel in imaging with red light. Thesecond white reference data G_(max) is an output value output from thelight-receiving device of each pixel in imaging with green light. Thethird white reference data B_(max) is an output value output from thelight-receiving device of each pixel in imaging with blue light. As thefirst white reference data R_(max), the second white reference dataG_(max), and the third white reference data B_(max), for example,voltage values can be used. The white subject used to acquire thereference data preferably has an extremely high reflectance.

The reference data may be acquired at the time of shipping of theimaging device and stored in the memory 73 in advance. For the memory73, a nonvolatile memory such as a flash memory is preferably used. Inaddition, the user may be allowed to rewrite the reference data whenusing the imaging device. The arithmetic circuit 71 has a function ofreading out the reference data stored in the memory 73. Specifically,the arithmetic circuit 71 has a function of reading out the referencedata from the memory 73 and correcting the image data of each color tothe correction image data with the use of the reference data. Thecorrection image data of each color may be output to the memory 73 andretained.

The first black reference data R_(min), the second black reference dataG_(min), the third black reference data B_(min), the first whitereference data R_(max), the second white reference data G_(max), and thethird white reference data B_(max) are preferably acquired for eachpixel 60. When the correction is performed on each pixel 60 using theacquired reference data, the correction can be less affected byvariations in the characteristics of the light-emitting devices and thelight-receiving devices. The average of all values in the imaging unit61 may be used for the first black reference data R_(min), the secondblack reference data G_(min), the third black reference data B_(min),the first white reference data R_(max), the second white reference dataG_(max), and the third white reference data B_(max). Using the averagevalues as the reference data can reduce the capacitance of the memory73.

In this specification and the like, the first black reference dataR_(min) and the first white reference data R_(max) are referred to asfirst reference data, the second black reference data G_(min) and thesecond white reference data G_(max) are referred to as second referencedata, and third black reference data B_(min) and third white referencedata B_(max) are referred to as reference data in some cases. The firstblack reference data R_(min), the second black reference data G_(min),the third black reference data B_(min), the first white reference dataR_(max), the second white reference data G_(max), and the third whitereference data B_(max) are referred to as reference data in some cases.

Calculation of the first correction image data R_(LSB), the secondcorrection image data G_(LSB), and the third correction image dataB_(LSB) using the reference data is described.

The first image data R_(X), the second image data G_(X), and the thirdimage data B_(X) output from the light-receiving device are convertedinto the first correction image data R_(LSB) according to the followingformula (1), the second correction image data G_(LSB) according to thefollowing formula (2), and the third correction image data B_(LSB)according to the following formula (3), respectively.

R _(LSB)=(R _(X) −R _(min))/(R _(max) −R _(min))×A:  (1)

G _(LSB)=(G _(X) −G _(min))/(G _(max) −G _(min))×A:  (2)

B _(LSB)=(B _(X) −B _(min))/(B _(max) −B _(min))×A:  (3)

Here, a constant A denotes the maximum gray level possible for asynthesized image SyIM. When the number of bits in the synthesized imageSyIM is n, the gray level of the synthesized image SyIM is an integergreater than or equal to 0 and less than or equal to 2^(n)−1 and theconstant A is 2^(n)−1. For example, when the number of bits in thesynthesized image SyIM is 8, the gray level of the synthesized imageSyIM is an integer greater than or equal to 0 and less than or equal to255 and the constant A is 255. While the first image data R_(X), thesecond image data G_(X), and the third image data B_(X) output from thelight-receiving device are analog values, the first correction imagedata R_(LSB), the second correction image data G_(LSB), and the thirdcorrection image data B_(LSB) are digital values.

The arithmetic circuit 71 combines the first correction image dataR_(LSB), the second correction image data G_(LSB), and the thirdcorrection image data B_(LSB) to generate the synthesized image data;thus, the color synthesized image SyIM can be generated.

In this manner, image data of each color is corrected using the whitereference data and the black reference data to generate the synthesizedimage SyIM. The imaging device can thus achieve high colorreproducibility.

Although the example in which the reference data acquired by imaging thesubject for the white reference and the subject for the black referenceis used for the correction, one embodiment of the present invention isnot limited thereto. The specific value determined from thecharacteristics of the light-receiving device may be used as thereference data. Reference data with a temperature as a variable may beemployed by acquiring the temperature in the imaging device or thetemperature in the usage environment. Using the reference data with atemperature as a variable can reduce the influence of temperature at thetime of imaging; accordingly, even when the characteristics of thelight-emitting device and the light-receiving device change depending ontemperature, the imaging device can achieve high color reproducibility.Reference data with cumulative driving times as variables may beemployed by acquiring the cumulative driving time of the light-emittingdevice and the cumulative driving time of the light-receiving device.With the use of reference data with cumulative operating time asvariables, even when the characteristics of the light-emitting deviceand light-receiving photon change depending on cumulative driving times,the imaging device can achieve high color reproducibility.

<Operation Example of Imaging Device>

An operation of the imaging device of one embodiment of the presentinvention is described with reference to FIG. 5. FIG. 5 is a flow chartshowing an operation of the imaging device.

In Step S11, the light-emitting device 91R that emits red light isturned on. Preferably, all the light-emitting devices 91R included inthe imaging unit 61 are turned on in this step.

In Step S12, the first image IM_(R) is formed by imaging using thelight-receiving device 91PD. Since the imaging proceeds while thelight-emitting device 91R is emitting light, the red light is reflectedby the subject and the reflected light enters the light-receiving device91PD. This means that the first image IM_(R) is information on the redcolor of the subject. In addition, the signal from the light-receivingdevice 91PD in each pixel (hereinafter, referred to as first image dataR_(X)) is output to the arithmetic circuit 71. The first image dataR_(X) is data corresponding to the value of current flowing to thelight-receiving device 91PD in each pixel, and output to the arithmeticcircuit 71 from the imaging unit 61 through the circuit portion 65. Asthe first image data R_(X), a voltage value can be used, for example.

In Step S13, the light-emitting device 91R is turned off. Preferably,all the light-emitting devices 91R included in the imaging unit 61 areturned off.

As Step S21, by the arithmetic circuit 71, the first image data R_(X) iscorrected using the reference data, and the first correction image dataR_(LSB) is calculated. The first correction image data R_(LSB) is outputto the memory 73 and retained. The reference data, which is retained inthe memory 73, is read out to the arithmetic circuit 71 at the time ofthe correction. As the reference data, the first white reference dataR_(max) and the first black reference data R_(min) can be used.

In Step S31, the light-emitting device 91G that emits green light isturned on. Preferably, all the light-emitting devices 91G included inthe imaging unit 61 are turned on in this step.

In Step S32, the second image IM_(G) is formed by imaging using thelight-receiving device 91PD. Since the imaging proceeds while thelight-emitting device 91G is emitting light, the green light isreflected by the subject and the reflected light enters thelight-receiving device 91PD. This means that the second image IM_(G) isinformation on the green color of the subject. In addition, the signalfrom the light-receiving device 91PD in each pixel (hereinafter,referred to as second image data G_(X)) is output to the arithmeticcircuit 71. The second image data G_(X) is data corresponding to thevalue of current flowing to the light-receiving device 91PD in eachpixel, and output to the arithmetic circuit 71 from the imaging unit 61through the circuit portion 65. As the second image data G_(X), avoltage value can be used, for example.

In Step S33, the light-emitting device 91G is turned off. Preferably,all the light-emitting devices 91G included in the imaging unit 61 areturned off.

As Step S41, by the arithmetic circuit 71, the second image data G_(X)is corrected using the reference data, and the second correction imagedata G_(LSB) is calculated. The second correction image data G_(LSB) isoutput to the memory 73 and retained. As the reference data, the secondwhite reference data G_(max) and the second black reference data G_(min)can be used.

In Step S51, the light-emitting device 91B that emits blue light isturned on. Preferably, all the light-emitting devices 91B included inthe imaging unit 61 are turned on in this step.

In Step S52, the third image IM_(B) is formed by imaging using thelight-receiving device 91PD. Since the imaging proceeds while thelight-emitting device 91B is emitting light, the blue light is reflectedby the subject and the reflected light enters the light-receiving device91PD. This means that the third image IM_(B) is information on the bluecolor of the subject. In addition, the signal from the light-receivingdevice 91PD in each pixel (hereinafter, referred to as third image dataB_(X)) is output to the arithmetic circuit 71. The third image dataB_(X) is data corresponding to the value of current flowing to thelight-receiving device 91PD in each pixel, and output to the arithmeticcircuit 71 from the imaging unit 61 through the circuit portion 65. Asthe third image data B_(X), a voltage value can be used, for example.

In Step S53, the light-emitting device 91B is turned off. Preferably,all the light-emitting devices 91B included in the imaging unit 61 areturned off.

As Step S61, by the arithmetic circuit 71, the third image data B_(X) iscorrected using the reference data, and the third correction image dataB_(LSB) is calculated. The third correction image data B_(LSB) is outputto the memory 73 and retained. As the reference data, the third whitereference data B_(max) and the third black reference data B_(min) can beused.

As Step S71, from the memory 73, the first correction image dataR_(LSB), the second correction image data G_(LSB), and the thirdcorrection image data B_(LSB) are read out to the arithmetic circuit 71,and combined to generate the synthesized image data; thus, the colorsynthesized image SyIM can be generated.

In this manner, image data of each color is corrected using the whitereference data and the black reference data. The imaging device can thusachieve high color reproducibility.

Although FIG. 5 shows an example in which imaging is performed in theorder of red, green, and blue, there is no particular limitation on thekinds of colors, the number of colors, and the order of colors forimaging.

Structure Example 2 of Imaging Device

Detailed structures of the imaging device of one embodiment of thepresent invention are described with reference to FIG. 6 to FIG. 10.

[Imaging Device 10A]

FIG. 6A shows a cross-sectional view of an imaging device 10A.

The imaging device 10A includes a light-receiving device 110 and alight-emitting device 190.

The light-receiving device 110 includes a pixel electrode 111, a commonlayer 112, an active layer 113, a common layer 114, and a commonelectrode 115.

The light-emitting device 190 includes a pixel electrode 191, the commonlayer 112, a light-emitting layer 193, the common layer 114, and thecommon electrode 115.

The pixel electrode 111, the pixel electrode 191, the common layer 112,the active layer 113, the light-emitting layer 193, the common layer114, and the common electrode 115 may each have a single-layer structureor a stacked-layer structure.

The pixel electrode 111 and the pixel electrode 191 are positioned overan insulating layer 214. The pixel electrode 111 and the pixel electrode191 can be formed using the same material in the same step.

The common layer 112 is positioned over the pixel electrode 111 and thepixel electrode 191. The common layer 112 is shared by thelight-receiving device 110 and the light-emitting device 190.

The active layer 113 overlaps with the pixel electrode 111 with thecommon layer 112 therebetween. The light-emitting layer 193 overlapswith the pixel electrode 191 with the common layer 112 therebetween. Theactive layer 113 contains a first organic compound, and thelight-emitting layer 193 contains a second organic compound that isdifferent from the first organic compound.

The common layer 114 is positioned over the common layer 112, the activelayer 113, and the light-emitting layer 193. The common layer 114 isshared by the light-receiving device 110 and the light-emitting device190.

The common electrode 115 includes a portion overlapping with the pixelelectrode 111 with the common layer 112, the active layer 113, and thecommon layer 114 therebetween. The common electrode 115 further includesa portion overlapping with the pixel electrode 191 with the common layer112, the light-emitting layer 193, and the common layer 114therebetween. The common electrode 115 is shared by the light-receivingdevice 110 and the light-emitting device 190.

In the imaging device of this embodiment, an organic compound is usedfor the active layer 113 of the light-receiving device 110. Thelight-receiving device 110 can have such a structure that the layersother than the active layer 113 are shared with the light-emittingdevice 190 (the EL element). Therefore, the light-receiving device 110can be formed concurrently with the formation of the light-emittingdevice 190 only by adding a step of depositing the active layer 113 inthe manufacturing process of the light-emitting device 190. Thelight-emitting device 190 and the light-receiving device 110 can beformed over one substrate. Accordingly, the light-emitting device 190and the light-receiving device 110 can be incorporated into the imagingdevice without a significant increase in the number of manufacturingsteps.

The imaging device 10A shows an example in which the light-receivingdevice 110 and the light-emitting device 190 have a common structureexcept that the active layer 113 of the light-receiving device 110 andthe light-emitting layer 193 of the light-emitting device 190 areseparately formed. Note that the structures of the light-receivingdevice 110 and the light-emitting device 190 are not limited thereto.The light-receiving device 110 and the light-emitting device 190 mayinclude separately formed layers other than the active layer 113 and thelight-emitting layer 193 (see imaging devices 10K, 10L, and 10Mdescribed later). The light-receiving device 110 and the light-emittingdevice 190 preferably include at least one layer used in common (commonlayer). Thus, the light-emitting device 190 and the light-receivingdevice 110 can be incorporated into the imaging device without asignificant increase in the number of manufacturing steps.

The imaging device 10A includes the light-receiving device 110, thelight-emitting device 190, a transistor 41, a transistor 42, and thelike between a pair of substrates (a substrate 151 and a substrate 152).

In the light-receiving device 110, the common layer 112, the activelayer 113, and the common layer 114, which are positioned between thepixel electrode 111 and the common electrode 115, can each be referredto as an organic layer (a layer containing an organic compound). Thepixel electrode 111 preferably has a function of reflecting visiblelight. An end portion of the pixel electrode 111 is covered with a bank216. The common electrode 115 has a function of transmitting visiblelight.

The light-receiving device 110 has a function of sensing light.Specifically, the light-receiving device 110 is a photoelectricconversion device that receives light 22 incident from the outside ofthe imaging device 10A and converts the light 22 into an electricsignal. The light 22 can also be expressed as light that is emitted bythe light-emitting device 190 and then reflected by an object. The light22 may enter the light-receiving device 110 through a lens describedlater. The description in this embodiment is made so that the pixelelectrode 111 functions as an anode and the common electrode 115functions as a cathode to match the electrodes of the light-emittingdevice 190. In other words, the light-receiving device 110 is driven byapplication of reverse bias between the pixel electrode 111 and thecommon electrode 115, so that light incident on the light-receivingdevice 110 can be sensed and electric charge can be generated.

A light-blocking layer BM is provided on a surface of the substrate 152facing the substrate 151. The light-blocking layer BM has an opening ata position overlapping with the light-receiving device 110 and anopening at a position overlapping with the light-emitting device 190.Providing the light-blocking layer BM can control the range where thelight-receiving device 110 senses light.

For the light-blocking layer BM, a material that blocks light emittedfrom the light-emitting device can be used. The light-blocking layer BMpreferably absorbs visible light. As the light-blocking layer BM, ablack matrix can be formed using a metal material or a resin materialcontaining pigment (e.g., carbon black) or dye, for example. Thelight-blocking layer BM may have a stacked-layer structure of a redcolor filter, a green color filter, and a blue color filter.

Here, the light-receiving device 110 senses light that is emitted by thelight-emitting device 190 and then reflected by an object. However, insome cases, light emitted from the light-emitting device 190 isreflected inside the imaging device 10A and enters the light-receivingdevice 110 without via an object, in some cases. The light-blockinglayer BM can reduce the influence of such stray light. For example, inthe case where the light-blocking layer BM is not provided, light 23 aemitted from the light-emitting device 190 is reflected by the substrate152 and reflected light 23 b is incident on the light-receiving device110 in some cases. Providing the light-blocking layer BM can inhibitentry of the reflected light 23 b into the light-receiving device 110.Consequently, noise can be reduced, and the sensitivity of a sensorusing the light-receiving device 110 can be increased.

In the light-emitting device 190, the common layer 112, thelight-emitting layer 193, and the common layer 114, which are positionedbetween the pixel electrode 191 and the common electrode 115, can eachbe referred to as an EL layer. The pixel electrode 191 preferably has afunction of reflecting visible light. An end portion of the pixelelectrode 191 is covered with the bank 216. The pixel electrode 111 andthe pixel electrode 191 are electrically insulated from each other bythe bank 216. The common electrode 115 has a function of transmittingvisible light.

The light-emitting device 190 has a function of emitting visible light.Specifically, the light-emitting device 190 is an electroluminescentelement that emits light (see light emission 21) to the substrate 152side by applying voltage between the pixel electrode 191 and the commonelectrode 115.

It is preferable that the light-emitting layer 193 be formed not tooverlap with a light-receiving region of the light-receiving device 110.Accordingly, it is possible to inhibit the light-emitting layer 193 fromabsorbing the light 22, so that the amount of light with which thelight-receiving device 110 is irradiated can be increased.

The pixel electrode 111 is electrically connected to a source or a drainof the transistor 41 through an opening provided in the insulating layer214. The end portion of the pixel electrode 111 is covered with the bank216.

The pixel electrode 191 is electrically connected to a source or a drainof the transistor 42 through an opening provided in the insulating layer214. The end portion of the pixel electrode 191 is covered with the bank216. The transistor 42 has a function of controlling the driving of thelight-emitting device 190.

The transistor 41 and the transistor 42 are on and in contact with thesame layer (the substrate 151 in FIG. 6A).

At least part of a circuit electrically connected to the light-receivingdevice 110 is preferably formed using the same material in the samesteps as a circuit electrically connected to the light-emitting device190. In that case, the thickness of the imaging device can be smallerthan that in the case where the two circuits are formed on differentplanes, and the manufacturing steps can be simplified.

The light-receiving device 110 and the light-emitting device 190 arepreferably covered with a protective layer 195. In FIG. 6A, theprotective layer 195 is provided on and in contact with the commonelectrode 115. Providing the protective layer 195 can inhibit entry ofimpurities such as water into the light-receiving device 110 and thelight-emitting device 190, so that the reliability of thelight-receiving device 110 and the light-emitting device 190 can beincreased. The protective layer 195 and the substrate 152 are attachedto each other with an adhesive layer 142.

Note that as shown in FIG. 7A, the protective layer is not necessarilyprovided over the light-receiving device 110 and the light-emittingdevice 190. In FIG. 7A, the common electrode 115 and the substrate 152are attached to each other with the adhesive layer 142.

[Imaging Device 10B]

FIG. 6B shows a cross-sectional view of an imaging device 10B that has astructure different from that of the above imaging device 10A. In thedescription of the imaging device below, components similar to those ofthe above-mentioned imaging device are not described in some cases.

The imaging device 10B illustrated in FIG. 6B includes a lens 149 inaddition to the components of the imaging device 10A.

The imaging device of this embodiment may include the lens 149. The lens149 is provided at a position overlapping with the light-receivingdevice 110. In the imaging device 10B, the lens 149 is provided incontact with the substrate 152. The lens 149 included in the imagingdevice 10B has a convex surface facing the substrate 151. Alternatively,the lens 149 may have a convex surface facing the substrate 152.

In the case where the light-blocking layer BM and the lens 149 areformed on the same plane of the substrate 152, their formation order isnot limited. FIG. 6B shows an example in which the lens 149 is formedfirst; alternatively, the light-blocking layer BM may be formed first.In FIG. 6B, an end portion of the lens 149 is covered with thelight-blocking layer BM.

In the imaging device 10B, the light 22 is incident on thelight-receiving device 110 through the lens 149. With the lens 149, theimaging range of the light-receiving device 110 can be narrowed ascompared to the case where the lens 149 is not provided, therebyinhibiting overlap of the imaging ranges between the adjacentlight-receiving devices 110. Thus, a clear image with little blurringcan be captured. Given that the imaging range of the light-receivingdevice 110 does not change, the lens 149 allows the size of a pinhole(corresponding to the size of an opening in BM that overlaps with thelight-receiving device 110 in FIG. 6B) to be increased, compared to thecase where the lens 149 is not provided. Hence, providing the lens 149can increase the amount of light entering the light-receiving device110.

Each of imaging devices illustrated in FIG. 7B and FIG. 7C has astructure in which the light 22 enters the light-receiving device 110through the lens 149, in a manner similar to that of the imaging device10B illustrated in FIG. 6B.

In FIG. 7B, the lens 149 is provided in contact with a top surface ofthe protective layer 195. The lens 149 included in the imaging deviceillustrated in FIG. 7B has a convex surface facing the substrate 152.

In the imaging device illustrated in FIG. 7C, a lens array 146 isprovided on the imaging surface side of the substrate 152. A lensincluded in the lens array 146 is provided at a position overlappingwith the light-receiving device 110. The light-blocking layer BM ispreferably provided on a surface of the substrate 152 facing thesubstrate 151.

As a method for forming the lens used in the imaging device of thisembodiment, a lens such as a microlens may be formed directly over thesubstrate or the light-receiving device, or a lens array formedseparately, such as a microlens array, may be attached to the substrate.

[Imaging Device 10C]

FIG. 6C shows a cross section of an imaging device 10C.

The imaging device 10C illustrated in FIG. 6C differs from the imagingdevice 10A in that the substrate 151, the substrate 152, and the bank216 are not included but a substrate 153, a substrate 154, an adhesivelayer 155, an insulating layer 212, and a bank 217 are included.

The substrate 153 and the insulating layer 212 are attached to eachother with the adhesive layer 155. The substrate 154 and the protectivelayer 195 are attached to each other with the adhesive layer 142.

The imaging device 10C is formed in such a manner that the insulatinglayer 212, the transistor 41, the transistor 42, the light-receivingdevice 110, the light-emitting device 190, and the like, which areformed over a formation substrate, are transferred onto the substrate153. The substrate 153 and the substrate 154 are preferably flexible.Accordingly, the flexibility of the imaging device 10C can be increased.For example, a resin is preferably used for each of the substrate 153and the substrate 154.

For each of the substrate 153 and the substrate 154, a polyester resinsuch as polyethylene terephthalate (PET) or polyethylene naphthalate(PEN), a polyacrylonitrile resin, an acrylic resin, a polyimide resin, apolymethyl methacrylate resin, a polycarbonate (PC) resin, a polyethersulfone (PES) resin, a polyamide resin (e.g., nylon or aramid), apolysiloxane resin, a cycloolefin resin, a polystyrene resin, apolyamide-imide resin, a polyurethane resin, a polyvinyl chloride resin,a polyvinylidene chloride resin, a polypropylene resin, apolytetrafluoroethylene (PTFE) resin, an ABS resin, or cellulosenanofiber can be used, for example. Glass that is thin enough to haveflexibility may be used for one or both of the substrate 153 and thesubstrate 154.

As the substrate included in the imaging device of this embodiment, afilm having high optical isotropy may be used. Examples of a highlyoptically isotropic film include a triacetyl cellulose (TAC, alsoreferred to as cellulose triacetate) film, a cycloolefin polymer (COP)film, a cycloolefin copolymer (COC) film, and an acrylic film.

The bank 217 preferably absorbs light emitted from the light-emittingdevice. As the bank 217, a black matrix can be formed using a resinmaterial containing a pigment or dye, for example. Moreover, the bank217 can be formed of a colored insulating layer by using a brown resistmaterial.

In some cases, light 23 c emitted from the light-emitting device 190 isreflected by the substrate 154 and the bank 217 and reflected light 23 dis incident on the light-receiving device 110, in some cases. In othercases, the light 23 c passes through the bank 217 and is reflected by atransistor, a wiring, or the like, and thus reflected light is incidenton the light-receiving device 110 in some cases. When the bank 217absorbs the light 23 c, the reflected light 23 d can be inhibited frombeing incident on the light-receiving device 110. Consequently, noisecan be reduced, and the sensitivity of a sensor using thelight-receiving device 110 can be increased.

The bank 217 preferably absorbs at least light having a wavelength thatis sensed by the light-receiving device 110. For example, in the casewhere the light-receiving device 110 senses green light emitted from thelight-emitting device 190, the bank 217 preferably absorbs at leastgreen light. For example, when the bank 217 includes a red color filter,the bank 217 can absorb the green light 23 c and thus the reflectedlight 23 d can be inhibited from being incident on the light-receivingdevice 110.

[Imaging Device 10D]

FIG. 8A shows a cross section of an imaging device 10D.

The imaging device 10D includes a colored layer 148 a in addition to thecomponents of the display unit 10B.

The colored layer 148 a includes a portion in contact with a top surfaceof the pixel electrode 111 in the light-receiving device 110 and aportion in contact with a side surface of the bank 216.

The colored layer 148 a preferably absorbs light emitted by thelight-emitting device. As the colored layer 148 a, a black matrix can beformed using a resin material containing a pigment or dye, for example.Moreover, the colored layer 148 a can be formed of a colored insulatinglayer by using a brown resist material.

The colored layer 148 a preferably absorbs at least light having awavelength that is sensed by the light-receiving device 110. Forexample, in the case where the light-receiving device 110 senses greenlight emitted from the light-emitting device 190, the colored layer 148a preferably absorbs at least green light. For example, when including ared color filter, the colored layer 148 a can absorb green light, andthus stray light (reflected light) can be inhibited from entering thelight-receiving device 110.

When the colored layer 148 a absorbs stray light generated in theimaging device 10D, the amount of stray light entering thelight-receiving device 110 can be reduced. Consequently, noise can bereduced, and the sensitivity of a sensor using the light-receivingdevice 110 can be increased.

In the imaging device of this embodiment, the colored layer is providedbetween the light-receiving device 110 and the light-emitting device190. This can inhibit stray light from entering the light-receivingdevice 110 from the light-emitting device 190.

[Imaging Device 10E]

FIG. 8B shows a cross section of an imaging device 10E.

The imaging device 10E includes a colored layer 148 b in addition to thecomponents of the imaging device 10D. A material that can be used forthe colored layer 148 b is the same as that used for the colored layer148 a.

The colored layer 148 b includes a portion in contact with a top surfaceof the pixel electrode 191 in the light-emitting device 190 and aportion in contact with a side surface of the bank 216.

The imaging device of this embodiment preferably includes one or both ofthe colored layer 148 a and the colored layer 148 b.

With both the colored layer 148 a and the colored layer 148 b, theamount of stray light entering the light-receiving device 110 can befurther reduced.

Note that in the imaging device 10E, the colored layer 148 b is incontact with a top surface of the pixel electrode 191; thus, the amountof light 21 that is emitted from the light-emitting device 190 andextracted to the outside of the imaging device 10E is smaller than thatin the case of the imaging device 10D (FIG. 8A) in some cases.Therefore, in the case where only one of the colored layer 148 a and thecolored layer 148 b is provided, only the colored layer 148 a ispreferably provided on the light-receiving device 110 side as in theimaging device 10D. This can increase the light extraction efficiency ofthe light-emitting device 190 and inhibits entry of stray light into thelight-receiving device 110. Thus, the imaging device can form ahigh-quality image by imaging.

[Imaging Device 10F]

FIG. 8C shows a cross section of an imaging device 10F.

The imaging device 10F includes a colored layer 148 in addition to thecomponents of the imaging device 10B. A material that can be used forthe colored layer 148 is the same as that used for the colored layer 148a.

The colored layer 148 is provided to cover a top surface and a sidesurface of the bank 216. The colored layer 148 includes a portion incontact with a top surface of the pixel electrode 111 in thelight-emitting device 110 and a portion in contact with a top surface ofthe pixel electrode 191 in the light-emitting device 190.

It is not necessary that the colored layer 148 a and the colored layer148 b shown in FIG. 8B are isolated from each other, and they may be onefilm as the colored layer 148 as shown in FIG. 8C. When the coloredlayer 148 absorbs stray light generated in the imaging device 10F, theamount of stray light entering the light-receiving device 110 can bereduced. Consequently, noise can be reduced, and the sensitivity of asensor using the light-receiving device 110 can be increased.

[Imaging Device 10G]

FIG. 9A shows a cross section of an imaging device 10G.

The imaging device 10G includes a colored layer 147 in addition to thecomponents of the imaging device 10B.

The colored layer 147 is positioned over the insulating layer 214, andthe bank 216 covers a top surface and a side surface of the coloredlayer 147. The colored layer 147 and the light-receiving device 110 areelectrically isolated from each other with the bank 216. In a similarmanner, the colored layer 147 and the light-emitting device 190 areelectrically isolated from each other with the bank 216.

A material that can be used for the colored layer 147 is the same asthat used for the colored layer 148 a. As in the above-described casesof the colored layers 148, 148 a, and 148 b, the colored layer 147absorbs stray light generated in the imaging device 10G, whereby theamount of stray light entering the light-receiving device 110 can bereduced. Consequently, noise can be reduced, and the sensitivity of asensor using the light-receiving device 110 can be increased.

The above-described colored layers 148, 148 a, and 148 b may have lowerresistivity than the bank 216, depending on materials thereof, becausethe colored layers are formed to absorb light. For example, theresistivity of a resin containing a pigment such as carbon is lower thanthat of a resin not containing the pigment. Thus, when any of thecolored layers 148, 148 a, and 148 b is provided, current leakage mayoccur in an adjacent light-emitting device or light-emitting device. Forexample, current leaking to an adjacent light-emitting device causes aproblem in that an undesired light-emitting device emits light (theproblem is also referred to as cross-talk).

Meanwhile, the colored layer 147 is provided apart from each of thelight-receiving device 110 and the light-emitting device 190. Thecolored layer 147 is electrically isolated from each of thelight-receiving device 110 and the light-emitting device 190 with thebank 216. Thus, even when the colored layer 147 has low resistivity, thelight-emitting device 110 and the light-emitting device 190 are lesslikely to be affected by the colored layer, which is preferable becausethe range of choices for materials used in the colored layer 147 iswidened. A black matrix may be formed using a metal material or thelike, for example, as the colored layer 147.

[Imaging Device 10H]

FIG. 9B shows a cross section of an imaging device 10H.

The imaging device 10H includes a colored layer 148 c in addition to thecomponents of the imaging device 10B.

In the imaging device 10H, the bank 216 has an opening reaching theinsulating layer 214. The colored layer 148 c includes a portion incontact with the insulating layer 214 through the opening, a portion incontact with a side surface of the bank 216 inside the opening, and aportion in contact with a top surface of the bank 216. The colored layer148 c and the light-receiving device 110 are electrically isolated fromeach other with the bank 216. In a similar manner, the colored layer 148c and the light-emitting device 190 are electrically isolated from eachother with the bank 216.

A material that can be used for the colored layer 148 c is the same asthat of the colored layer 147. When the colored layer 148 c absorbsstray light generated in the imaging device 10H, the amount of straylight entering the light-receiving device 110 can be reduced.Consequently, noise can be reduced, and the sensitivity of a sensorusing the light-receiving device 110 can be increased.

The colored layer 148 c is provided apart from each of thelight-receiving device 110 and the light-emitting device 190. Inaddition, the colored layer 148 c is electrically isolated from each ofthe light-receiving device 110 and the light-emitting device 190 withthe bank 216. Thus, even when the colored layer 148 c has lowresistivity, the light-emitting device 110 and the light-emitting device190 are less likely to be affected by the colored layer, which ispreferable because the range of choices for materials used for thecolored layer 148 c is widened.

[Imaging Device 10J]

FIG. 9C shows a cross section of an imaging device 10J.

The imaging device 10J includes a colored layer 148 c in addition to thecomponents of the imaging device 10D.

As illustrated in FIG. 8A to FIG. 8C and FIG. 9A to FIG. 9C, the imagingdevice of one embodiment of the present invention preferably includesone or more of the colored layers 148, 148 a, 148 b, 148 c, and 147.This enables absorption of stray light generated in the imaging deviceand reduction of the amount of stray light entering the light-receivingdevice 110. Consequently, noise can be reduced, and the sensitivity of asensor using the light-receiving device 110 can be increased.

[Imaging Devices 10K, 10L, 10M]

FIG. 10A shows a cross section of an imaging device 10K, FIG. 10B showsa cross section of an imaging device 10L, and FIG. 10C shows a crosssection of an imaging device 10M.

The imaging device 10K differs from the imaging device 10A in that thecommon layer 114 is not included and a buffer layer 184 and a bufferlayer 194 are included. The buffer layer 184 and the buffer layer 194may each have a single-layer structure or a stacked-layer structure.

In the imaging device 10K, the light-receiving device 110 includes thepixel electrode 111, the common layer 112, the active layer 113, thebuffer layer 184, and the common electrode 115. In the imaging device10K, the light-emitting device 190 includes the pixel electrode 191, thecommon layer 112, the light-emitting layer 193, the buffer layer 194,and the common electrode 115.

The imaging device 10L differs from the imaging device 10A in that thecommon layer 112 is not included and a buffer layer 182 and a bufferlayer 192 are included. The buffer layer 182 and the buffer layer 192may each have a single-layer structure or a stacked-layer structure.

In the imaging device 10L, the light-receiving device 110 includes thepixel electrode 111, the buffer layer 182, the active layer 113, thecommon layer 114, and the common electrode 115. In the imaging device10L, the light-emitting device 190 includes the pixel electrode 191, thebuffer layer 192, the light-emitting layer 193, the common layer 114,and the common electrode 115.

The imaging device 10M differs from the imaging device 10A in that thecommon layer 112 and the common layer 114 are not included and thebuffer layers 182, 184, 192, and 194 are included.

In the imaging device 10M, the light-receiving device 110 includes thepixel electrode 111, the buffer layer 182, the active layer 113, thebuffer layer 184, and the common electrode 115. In the imaging device10M, the light-emitting device 190 includes the pixel electrode 191, thebuffer layer 192, the light-emitting layer 193, the buffer layer 194,and the common electrode 115.

Other layers as well as the active layer 113 and the light-emittinglayer 193 can be formed separately when the light-receiving device 110and the light-emitting device 190 are manufactured.

The imaging device 10K shows an example in which the buffer layer 184between the common electrode 115 and the active layer 113 and the bufferlayer 194 between the common electrode 115 and the light-emitting layer193 are formed separately. As the buffer layer 184, for example, anelectron-transport layer can be formed. As the buffer layer 194, one orboth of an electron-injection layer and an electron-transport layer canbe formed, for example.

The imaging device 10L shows an example in which the buffer layer 182between the pixel electrode 111 and the active layer 113 and the bufferlayer 192 between the pixel electrode 191 and the light-emitting layer193 are formed separately. As the buffer layer 182, for example, ahole-transport layer can be formed. As the buffer layer 192, one or bothof a hole-injection layer and a hole-transport layer can be formed, forexample.

The imaging device 10M shows an example in which in each of thelight-receiving device 110 and the light-emitting device 190, a commonlayer is not provided between the pair of electrodes (the pixelelectrode 111 or 191 and the common electrode 115). The light-receivingdevice 110 and the light-emitting device 190 included in the imagingdevice 10M can be manufactured in the following manner: the pixelelectrode 111 and the pixel electrode 191 are formed over the insulatinglayer 214 using the same material in the same step; the buffer layer182, the active layer 113, and the buffer layer 184 are formed over thepixel electrode 111; the buffer layer 192, the light-emitting layer 193,and the buffer layer 194 are formed over the pixel electrode 191; andthen, the common electrode 115 is formed to cover the pixel electrode111, the buffer layer 182, the active layer 113, the buffer layer 184,the pixel electrode 191, the buffer layer 192, the light-emitting layer193, and the buffer layer 194. Note that the manufacturing order of thestacked-layer structure of the buffer layer 182, the active layer 113,and the buffer layer 184 and the stacked-layer structure of the bufferlayer 192, the light-emitting layer 193, and the buffer layer 194 is notparticularly limited. For example, after the buffer layer 182, theactive layer 113, and the buffer layer 184 are formed, the buffer layer192, the light-emitting layer 193, and the buffer layer 194 may beformed. By contrast, the buffer layer 192, the light-emitting layer 193,and the buffer layer 194 may be formed before the buffer layer 182, theactive layer 113, and the buffer layer 184 are formed. Alternatively,the buffer layer 182, the buffer layer 192, the active layer 113, andthe light-emitting layer 193 may be formed in that order, for example.

Structure Example 3 of Imaging Device

A more detailed structure of the imaging device of one embodiment of thepresent invention will be described below with reference to FIG. 11 toFIG. 15.

[Imaging Device 100A]

FIG. 11 is a perspective view of an imaging device 100A, and FIG. 12 isa cross-sectional view of the imaging device 100A.

The imaging device 100A has a structure in which the substrate 152 andthe substrate 151 are bonded to each other. In FIG. 11, the substrate152 is denoted by a dashed line.

The imaging device 100A can also be referred to as an imaging moduleincluding any one or more of the imaging device of one embodiment of thepresent invention, a connector, and an integrated circuit (IC). As theconnector, a flexible printed circuit (FPC) board, a tape carrierpackage (TCP), or the like can also be used. The integrated circuit (IC)can be mounted on the imaging module by a COG (chip on glass) method, aCOF (chip on film) method, or the like. FIG. 11 shows an example inwhich an IC 173 and an FPC 172 are mounted on the imaging device 100A.The imaging device 100A includes an imaging unit 162, a circuit 164, awiring 165, and the like.

As the circuit 164, for example, a scan line driver circuit can be used.

The wiring 165 has a function of supplying a signal and power to theimaging unit 162 and the circuit 164. The signal and power are input tothe wiring 165 from the outside through the FPC 172 or from the IC 173.

FIG. 11 illustrates an example in which the IC 173 is provided over thesubstrate 151 by a COG method, a COF method, or the like. An ICincluding a scan line driver circuit, a signal line driver circuit, orthe like can be used as the IC 173, for example. Note that the imagingdevice 100A and the imaging module may have a structure that is notprovided with an IC. The IC may be implemented on the FPC by a COFmethod or the like.

FIG. 12 illustrates an example of a cross section including part of aregion including the FPC 172, part of a region including the circuit164, part of a region including the imaging unit 162, and part of aregion including an end portion of the imaging device 100A illustratedin FIG. 11.

The imaging device 100A in FIG. 12 includes a transistor 201, atransistor 205, a transistor 206, the light-emitting device 190, thelight-receiving device 110, and the like between the substrate 151 andthe substrate 152.

The substrate 152 and the insulating layer 214 are bonded to each otherwith an adhesive layer 142. A solid sealing structure, a hollow sealingstructure, or the like can be employed to seal the light-emitting device190 and the light-receiving device 110. In FIG. 12, a hollow sealingstructure is employed in which a space 143 surrounded by the substrate152, the adhesive layer 142, and the insulating layer 214 is filled withan inert gas (e.g., nitrogen or argon). The adhesive layer 142 mayoverlap with the light-emitting device 190. The space 143 surrounded bythe substrate 152, the adhesive layer 142, and the insulating layer 214may be filled with a resin different from that of the adhesive layer142.

The light-emitting device 190 has a stacked-layer structure in which thepixel electrode 191, the common layer 112, the light-emitting layer 193,the common layer 114, and the common electrode 115 are stacked in thisorder from the insulating layer 214 side. The pixel electrode 191 iselectrically connected to a conductive layer 222 b included in thetransistor 206 through an opening provided in the insulating layer 214.The transistor 206 has a function of controlling the driving of thelight-emitting device 190. An end portion of the pixel electrode 191 iscovered with the bank 216. The pixel electrode 191 includes a materialthat reflects visible light, and the common electrode 115 includes amaterial that transmits visible light.

The light-receiving device 110 has a stacked-layer structure in whichthe pixel electrode 111, the common layer 112, the active layer 113, thecommon layer 114, and the common electrode 115 are stacked in that orderfrom the insulating layer 214 side. The pixel electrode 111 iselectrically connected to the conductive layer 222 b included in thetransistor 205 through an opening provided in the insulating layer 214.An end portion of the pixel electrode 111 is covered with the bank 216.The pixel electrode 111 includes a material that reflects visible light,and the common electrode 115 includes a material that transmits visiblelight.

Light from the light-emitting device 190 is emitted toward the substrate152. Light enters the light-receiving device 110 through the substrate152 and the space 143. For the substrate 152, a material having a highvisible-light-transmitting property is preferably used.

The pixel electrode 111 and the pixel electrode 191 can be formed usingthe same material in the same step. The common layer 112, the commonlayer 114, and the common electrode 115 are used in both thelight-receiving device 110 and the light-emitting device 190. Thelight-receiving device 110 and the light-emitting device 190 can havecommon components except the active layer 113 and the light-emittinglayer 193. Thus, the light-receiving device 110 and the light-receivingdevice 110 can be incorporated into the imaging device 100A without asignificant increase in the number of manufacturing steps.

A light-blocking layer BM is provided on a surface of the substrate 152,which faces the substrate 151. The light-blocking layer BM has anopening at a position overlapping with the light-receiving device 110and an opening at a position overlapping with the light-emitting device190. Providing the light-blocking layer BM can control the range wherethe light-receiving device 110 senses light. Furthermore, with thelight-blocking layer BM, light emitted by the light-emitting device 190can be prevented from directly entering the light-receiving device 110without passing through any object. Hence, a sensor with less noise andhigh sensitivity can be obtained.

The transistor 201, the transistor 205, and the transistor 206 areformed over the substrate 151. These transistors can be fabricated usingthe same material in the same step.

An insulating layer 211, an insulating layer 213, an insulating layer215, and the insulating layer 214 are provided in this order over thesubstrate 151. Parts of the insulating layer 211 function as gateinsulating layers of the transistors. Parts of the insulating layer 213function as gate insulating layers of the transistors. The insulatinglayer 215 is provided to cover the transistors. The insulating layer 214is provided to cover the transistors and has a function of aplanarization layer. Note that the number of gate insulating layers andthe number of insulating layers covering the transistor are not limitedand either a single layer or two or more layers may be employed.

A material through which impurities such as water and hydrogen do noteasily diffuse is preferably used for at least one of the insulatinglayers that cover the transistors. Thus, such an insulating layer canserve as a barrier layer. Such a structure can effectively inhibitdiffusion of impurities into the transistors from the outside andincrease the reliability of the imaging device.

An inorganic insulating film is preferably used as each of theinsulating layers 211, 213, and 215. As the inorganic insulating film,for example, a silicon nitride film, a silicon oxynitride film, asilicon oxide film, a silicon nitride oxide film, an aluminum oxidefilm, or an aluminum nitride film, or the like can be used. A hafniumoxide film, an yttrium oxide film, a zirconium oxide film, a galliumoxide film, a tantalum oxide film, a magnesium oxide film, a lanthanumoxide film, a cerium oxide film, a neodymium oxide film, or the like mayalso be used. A stack including two or more of the above insulatingfilms may also be used.

Here, an organic insulating film often has a lower barrier property thanan inorganic insulating film. Therefore, the organic insulating filmpreferably has an opening in the vicinity of an end portion of theimaging device 100A. This can inhibit entry of impurities from the endportion of the imaging device 100A through the organic insulating film.Alternatively, the organic insulating film may be formed so that its endportion is positioned on the inner side compared to the end portion ofthe imaging device 100A, to prevent the organic insulating film frombeing exposed at the end portion of the imaging device 100A.

An organic insulating film is suitable for the insulating layer 214functioning as a planarization layer. Examples of materials which can beused for the organic insulating film include an acrylic resin, apolyimide resin, an epoxy resin, a polyamide resin, a polyimide-amideresin, a siloxane resin, a benzocyclobutene-based resin, a phenol resin,and precursors of these resins.

In a region 228 illustrated in FIG. 12, an opening is formed in theinsulating layer 214. This can inhibit entry of impurities into theimaging unit 162 from the outside through the insulating layer 214 evenwhen an organic insulating film is used as the insulating layer 214.Consequently, the imaging device 100A can have higher reliability.

Each of the transistors 201, 205, and 206 includes a conductive layer221 functioning as a gate, the insulating layer 211 functioning as thegate insulating layer, a conductive layer 222 a and the conductive layer222 b functioning as a source and a drain, a semiconductor layer 231,the insulating layer 213 functioning as the gate insulating layer, aconductive layer 223 functioning as a gate. Here, a plurality of layersobtained by processing the same conductive film are shown with the samehatching pattern. The insulating layer 211 is positioned between theconductive layer 221 and the semiconductor layer 231. The insulatinglayer 213 is positioned between the conductive layer 223 and thesemiconductor layer 231.

There is no particular limitation on the structure of the transistorsincluded in the imaging device of this embodiment. For example, a planartransistor, a staggered transistor, or an inverted staggered transistorcan be used. A top-gate or a bottom-gate transistor structure may beemployed. Alternatively, gates may be provided above and below asemiconductor layer in which a channel is formed.

The structure in which the semiconductor layer where a channel is formedis provided between two gates is used for the transistors 201, 205, and206. The two gates may be connected to each other and supplied with thesame signal to operate the transistor. Alternatively, by supplying apotential for controlling the threshold voltage to one of the two gatesand a potential for driving to the other, the threshold voltage of thetransistor may be controlled.

There is no particular limitation on the crystallinity of asemiconductor material used for the transistors, and an amorphoussemiconductor or a semiconductor having crystallinity (amicrocrystalline semiconductor, a polycrystalline semiconductor, asingle-crystal semiconductor, or a semiconductor partly includingcrystal regions) may be used. A semiconductor having crystallinity ispreferably used, in which case deterioration of the transistorcharacteristics can be suppressed.

It is preferable that a semiconductor layer of a transistor contain ametal oxide (also referred to as an oxide semiconductor). Alternatively,the semiconductor layer of the transistor may contain silicon. Examplesof silicon include amorphous silicon and crystalline silicon (e.g.,low-temperature polysilicon or single crystal silicon).

The semiconductor layer preferably contains indium, M (M is one or morekinds selected from gallium, aluminum, silicon, boron, yttrium, tin,copper, vanadium, beryllium, titanium, iron, nickel, germanium,zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum,tungsten, and magnesium), and zinc, for example. Specifically, M ispreferably one or more kinds selected from aluminum, gallium, yttrium,and tin.

It is particularly preferable to use an oxide containing indium (In),gallium (Ga), and zinc (Zn) (also referred to as IGZO) for thesemiconductor layer.

In the case where the semiconductor layer is an In-M-Zn oxide, asputtering target used for depositing the In-M-Zn oxide preferably hasthe atomic proportion of In higher than or equal to the atomicproportion of M. Examples of the atomic ratio of the metal elements insuch a sputtering target include In:M:Zn=1:1:1, In:M:Zn=1:1:1.2,In:M:Zn=2:1:3, In:M:Zn=3:1:2, In:M:Zn=4:2:3, In:M:Zn=4:2:4.1,In:M:Zn=5:1:6, In:M:Zn=5:1:7, In:M:Zn=5:1:8, In:M:Zn=6:1:6, andIn:M:Zn=5:2:5.

A target containing a polycrystalline oxide is preferably used as thesputtering target, in which case the semiconductor layer havingcrystallinity is easily formed. Note that the atomic ratio between metalelements in the formed semiconductor layer may vary from the aboveatomic ratio between metal elements in the sputtering target in a rangeof ±40%. For example, in the case where the composition of a sputteringtarget used for the semiconductor layer is In:Ga:Zn=4:2:4.1 [atomicratio], the composition of the semiconductor layer to be formed is insome cases in the neighborhood of In:Ga:Zn=4:2:3 [atomic ratio].

Note that when the atomic ratio is described as In:Ga:Zn=4:2:3 or asbeing in the neighborhood thereof, the case is included where the atomicproportion of Ga is greater than or equal to 1 and less than or equal to3 and the atomic proportion of Zn is greater than or equal to 2 and lessthan or equal to 4 with the atomic proportion of In being 4. When theatomic ratio is described as In:Ga:Zn=5:1:6 or as being in theneighborhood thereof, the case is included where the atomic proportionof Ga is greater than 0.1 and less than or equal to 2 and the atomicproportion of Zn is greater than or equal to 5 and less than or equal to7 with the atomic proportion of In being 5. When the atomic ratio isdescribed as In:Ga:Zn=1:1:1 or as being in the neighborhood thereof, thecase is included where the atomic proportion of Ga is greater than 0.1and less than or equal to 2 and the atomic proportion of Zn is greaterthan 0.1 and less than or equal to 2 with the atomic proportion of Inbeing 1.

The transistor included in the circuit 164 and the transistor includedin the imaging unit 162 may have the same structure or differentstructures. One structure or two or more kinds of structures may beemployed for a plurality of transistors included in the circuit 164.Similarly, one structure or two or more kinds of structures may beemployed for a plurality of transistors included in the imaging unit162.

A connection portion 204 is provided in a region of the substrate 152not overlapping with the substrate 151. In the connection portion 204,the wiring 165 is electrically connected to the FPC 172 via a connectionlayer 242 and a conductive layer 166. On the top surface of theconnection portion 204, the conductive layer 166 obtained by processingthe same conductive film as the pixel electrode 191 is exposed. Thus,the connection portion 204 and the FPC 172 can be electrically connectedto each other through the connection layer 242.

Any of a variety of optical members can be arranged on the outer side ofthe substrate 152. Examples of the optical members include a polarizingplate, a retardation plate, a light diffusion layer (a diffusion film orthe like), an anti-reflective layer, and a light-condensing film.Furthermore, an antistatic film preventing the attachment of dust, awater repellent film suppressing the attachment of stain, a hard coatfilm inhibiting generation of a scratch caused by the use, a shockabsorbing layer or the like may be arranged on the outside of thesubstrate 152.

For each of the substrate 151 and the substrate 152, glass, quartz,ceramic, sapphire, a resin, or the like can be used. When a flexiblematerial is used for the substrate 151 and the substrate 152, theflexibility of the imaging device can be increased.

As the adhesive layer, a variety of curable adhesives, e.g., aphotocurable adhesive such as an ultraviolet curable adhesive, areactive curable adhesive, a thermosetting adhesive, and an anaerobicadhesive can be used. Examples of these adhesives include an epoxyresin, an acrylic resin, a silicone resin, a phenol resin, a polyimideresin, an imide resin, a PVC (polyvinyl chloride) resin, a PVB(polyvinyl butyral) resin, and an EVA (ethylene vinyl acetate) resin. Inparticular, a material with low moisture permeability, such as an epoxyresin, is preferred. Alternatively, a two-component resin may be used.An adhesive sheet or the like may be used.

As the connection layer 242, an anisotropic conductive film (ACF), ananisotropic conductive paste (ACP), or the like can be used.

The light-emitting device 190 may be a top emission, bottom emission, ordual emission light-emitting device, or the like. A conductive film thattransmits visible light is used as the electrode through which light isextracted. A conductive film that reflects visible light is preferablyused as the electrode through which no light is extracted.

The light-emitting device 190 includes at least the light-emitting layer193. In addition to the light-emitting layer 193, the light-emittingdevice 190 may further include a layer containing a substance with ahigh hole-injection property, a layer containing a substance with a highhole-transport property, a layer containing a hole-blocking material, alayer containing a substance with a high electron-transport property, alayer containing a substance with a high electron-injection property, alayer containing a substance with a bipolar property (a substance with ahigh electron- and hole-transport property), or the like. For example,the common layer 112 preferably includes one or both of a hole-injectionlayer and a hole-transport layer. For example, the common layer 114preferably includes one or both of an electron-transport layer and anelectron-injection layer.

Either a low molecular compound or a high molecular compound can be usedfor the common layer 112, the light-emitting layer 193, and the commonlayer 114 and an inorganic compound may also be contained. The layersthat constitute the common layer 112, the light-emitting layer 193, andthe common layer 114 can each be formed by a method such as anevaporation method (including a vacuum evaporation method), a transfermethod, a printing method, an inkjet method, or a coating method.

The light-emitting layer 193 may contain an inorganic compound such asquantum dots as a light-emitting material.

The active layer 113 of the light-receiving device 110 contains asemiconductor. Examples of the semiconductor include an inorganicsemiconductor such as silicon and an organic semiconductor including anorganic compound. This embodiment shows an example in which an organicsemiconductor is used as the semiconductor contained in the activelayer. The use of an organic semiconductor is preferable because thelight-emitting layer 193 of the light-emitting device 190 and the activelayer 113 of the light-receiving device 110 can be formed by the samemethod (e.g., a vacuum evaporation method) and thus the samemanufacturing apparatus can be used.

Examples of an n-type semiconductor material included in the activelayer 113 are electron-accepting organic semiconductor materials such asfullerene (e.g., C₆₀ and C₇₀) and derivatives thereof. As a p-typesemiconductor material included in the active layer 113, anelectron-donating organic semiconductor material such as copper(II)phthalocyanine (CuPc) or tetraphenyldibenzoperiflanthene (DBP) can begiven.

For example, the active layer 113 is preferably formed by co-evaporationof an n-type semiconductor and a p-type semiconductor.

As materials that can be used for conductive layers such as a variety ofwirings and electrodes that constitute an imaging device, in addition toa gate, a source, and a drain of a transistor, metals such as aluminum,titanium, chromium, nickel, copper, yttrium, zirconium, molybdenum,silver, tantalum, or tungsten, or an alloy containing any of thesemetals as its main component can be given. A film containing any ofthese materials can be used in a single layer or as a stacked-layerstructure.

As a light-transmitting conductive material, a conductive oxide such asindium oxide, indium tin oxide, indium zinc oxide, zinc oxide, or zincoxide containing gallium, or graphene can be used. Alternatively, ametal material such as gold, silver, platinum, magnesium, nickel,tungsten, chromium, molybdenum, iron, cobalt, copper, palladium, ortitanium, or an alloy material containing the metal material can beused. Further alternatively, a nitride of the metal material (e.g.,titanium nitride) or the like may be used. Note that in the case ofusing the metal material or the alloy material (or the nitride thereof),the thickness is preferably set small enough to be able to transmitlight. A stacked-layer film of any of the above materials can be usedfor the conductive layers. For example, when a stacked film of indiumtin oxide and an alloy of silver and magnesium, or the like is used, theconductivity can be increased, which is preferable. They can also beused for conductive layers such as a variety of wirings and electrodesthat constitute an imaging device, and conductive layers (conductivelayers functioning as a pixel electrode or a common electrode) includedin a light-receiving device.

As an insulating material that can be used for each insulating layer,for example, a resin such as acrylic or epoxy resin, and an inorganicinsulating material such as silicon oxide, silicon oxynitride, siliconnitride oxide, silicon nitride, or aluminum oxide can be given.

[Imaging Device 100B]

FIG. 13A shows a cross section of an imaging device 100B.

The imaging device 100B is different from the imaging device 100A mainlyin that the lens 149 and the protective layer 195 are included.

Providing the protective layer 195 covering the light-receiving device110 and the light-emitting device 190 can inhibit entry of impuritiessuch as water into the light-receiving device 110 and the light-emittingdevice 190, so that the reliability of the light-receiving device 110and the light-emitting device 190 can be increased.

In the region 228 in the vicinity of an end portion of the imagingdevice 100B, the insulating layer 215 and the protective layer 195 arepreferably in contact with each other through an opening in theinsulating layer 214. In particular, the inorganic insulating filmincluded in the insulating layer 215 and the inorganic insulating filmincluded in the protective layer 195 are preferably in contact with eachother. Thus, entry of impurities from the outside into the imaging unit162 through the organic insulating film can be inhibited. Consequently,the imaging device 100B can have higher reliability.

FIG. 13B illustrates an example in which the protective layer 195 has athree-layer structure. In FIG. 13B, the protective layer 195 includes aninorganic insulating layer 195 a over the common electrode 115, anorganic insulating layer 195 b over the inorganic insulating layer 195a, and an inorganic insulating layer 195 c over the organic insulatinglayer 195 b.

An end portion of the inorganic insulating layer 195 a and an endportion of the inorganic insulating layer 195 c extend beyond an endportion of the organic insulating layer 195 b and are in contact witheach other. The inorganic insulating layer 195 a is in contact with theinsulating layer 215 (inorganic insulating layer) through the opening inthe insulating layer 214 (organic insulating layer). Accordingly, thelight-receiving device 110 and the light-emitting device 190 can besurrounded by the insulating layer 215 and the protective layer 195,whereby the reliability of the light-receiving device 110 and thelight-emitting device 190 can be increased.

As described above, the protective layer 195 may have a stacked-layerstructure of an organic insulating film and an inorganic insulatingfilm. In that case, an end portion of the inorganic insulating layerpreferably extends beyond an end portion of the organic insulatinglayer.

The lens 149 is provided on the surface of the substrate 152, whichfaces the substrate 151. The lens 149 has the convex surface on thesubstrate 151 side. It is preferable that the light-receiving region ofthe light-receiving device 110 overlap with the lens 149 and do notoverlap with the light-emitting layer 193. Thus, the sensitivity andaccuracy of a sensor using the light-receiving device 110 can beincreased.

The lens 149 preferably has a refractive index greater than or equal to1.3 and less than or equal to 2.5. The lens 149 can be formed using atleast one of an inorganic material and an organic material. For example,a material containing a resin can be used for the lens 149. Moreover, amaterial containing at least one of an oxide and a sulfide can be usedfor the lens 149.

Specifically, a resin containing chlorine, bromine, or iodine, a resincontaining a heavy metal atom, a resin having an aromatic ring, a resincontaining sulfur, and the like can be used for the lens 149.Alternatively, a material containing a resin and nanoparticles of amaterial having a higher refractive index than the resin can be used forthe lens 149. Titanium oxide, zirconium oxide, or the like can be usedfor the nanoparticles.

Cerium oxide, hafnium oxide, lanthanum oxide, magnesium oxide, niobiumoxide, tantalum oxide, titanium oxide, yttrium oxide, zinc oxide, anoxide containing indium and tin, an oxide containing indium, gallium,and zinc, and the like can be used for the lens 149. Alternatively, zincsulfide and the like can be used for the lens 149.

In the imaging device 100B, the protective layer 195 and the substrate152 are bonded to each other with the adhesive layer 142. The adhesivelayer 142 is provided to overlap with the light-receiving device 110 andthe light-emitting device 190; that is, the imaging device 100B employsa solid sealing structure.

[Imaging Device 100C]

FIG. 14A shows a cross section of an imaging device 100C.

The imaging device 100C differs from the imaging device 100B intransistor structures.

The imaging device 100C includes a transistor 208, a transistor 209, anda transistor 210 over the substrate 151.

Each of the transistors 208, 209, and 210 includes the conductive layer221 functioning as a gate, the insulating layer 211 functioning as agate insulating layer, a semiconductor layer including a channelformation region 231 i and a pair of low-resistance regions 231 n, theconductive layer 222 a connected to one of the low-resistance regions231 n, the conductive layer 222 b connected to the other low-resistanceregion 231 n, an insulating layer 225 functioning as a gate insulatinglayer, the conductive layer 223 functioning as a gate, and theinsulating layer 215 covering the conductive layer 223. The insulatinglayer 211 is positioned between the conductive layer 221 and the channelformation region 231 i. The insulating layer 225 is positioned betweenthe conductive layer 223 and the channel formation region 231 i.

The conductive layer 222 a and the conductive layer 222 b are eachconnected to the corresponding low-resistance region 231 n throughopenings provided in the insulating layer 225 and the insulating layer215. One of the conductive layer 222 a and the conductive layer 222 bserves as a source, and the other serves as a drain.

The pixel electrode 191 of the light-emitting device 190 is electricallyconnected to one of the pair of low-resistance regions 231 n of thetransistor 208 through the conductive layer 222 b.

The pixel electrode 111 of the light-receiving device 110 iselectrically connected to the other of the pair of low-resistanceregions 231 n of the transistor 209 through the conductive layer 222 b.

In each of the transistor 208, the transistor 209, and the transistor210 illustrated in FIG. 14A, an example in which the insulating layer225 covers a top and side surfaces of the semiconductor layer isdescribed. Meanwhile, in the transistor 202 illustrated in FIG. 14B, theinsulating layer 225 overlaps with the channel formation region 231 i ofthe semiconductor layer 231 and does not overlap with the low-resistanceregions 231 n. The structure illustrated in FIG. 14B is obtained byprocessing the insulating layer 225 with the conductive layer 223 as amask, for example. In FIG. 14B, the insulating layer 215 is provided tocover the insulating layer 225 and the conductive layer 223, and theconductive layer 222 a and the conductive layer 222 b are connected tothe low-resistance regions 231 n through the openings in the insulatinglayer 215. Furthermore, an insulating layer 218 covering the transistormay be provided.

The imaging device 100C is different from the imaging device 100B inthat a colored layer 147 is included.

The colored layer 147 is positioned over the insulating layer 214 andthe bank 216 covers the top surface and the side surface of the coloredlayer 147.

In FIG. 14A, the colored layer 147 and the light-receiving device 110are provided apart from each other. Similarly, the colored layer 147 andthe light-emitting device 190 are provided apart from each other. Theposition of the colored layer 147 is not limited to the arrangementshown in FIG. 14A. As shown in FIG. 14C, the colored layer 147 may coverone or both of an end portion of the pixel electrode 111 and an endportion of the pixel electrode 191.

In FIG. 14A, the colored layer 147 is provided apart from thelight-receiving device 110 and the light-emitting device 190. Thus, thecolored layer 147 is less likely to affect the light-receiving device110 and the light-emitting device 190 even when having low resistivity,which is preferable because the range of choices for materials used forthe colored layer 147 is widen.

In FIG. 14C, the colored layer 147 covers the end portion of the pixelelectrode 111 and the end portion of the pixel electrode 191;accordingly, the area of the colored layer 147 can be increased. Thelarger the area where the colored layer 147 is provided is, the morestray light generated in the imaging device is absorbed by the coloredlayer 147, which is preferable because the amount of stray lightentering the light-receiving device 110 can be reduced. Consequently,noise can be reduced, and the sensitivity of a sensor using thelight-receiving device 110 can be increased.

[Imaging Device 100D]

FIG. 15 shows a cross section of an imaging device 100D.

The imaging device 100D is different from the imaging device 100C inthat the colored layer 147 is not included but the colored layer 148 ais included.

The colored layer 148 a includes a portion in contact with a top surfaceof the pixel electrode 111 in the light-receiving device 110 and aportion in contact with a side surface of the bank 216.

When the colored layer 148 a absorbs stray light generated in theimaging device 100D, the amount of stray light entering thelight-receiving device 110 can be reduced. Consequently, noise can bereduced, and the sensitivity of a sensor using the light-receivingdevice 110 can be increased.

In addition, the imaging device 100D differs from the imaging device100C in that neither the substrate 151 nor the substrate 152 is includedand that the substrate 153, the substrate 154, the adhesive layer 155,and the insulating layer 212 are included.

The substrate 153 and the insulating layer 212 are attached to eachother with the adhesive layer 155. The substrate 154 and the protectivelayer 195 are attached to each other with the adhesive layer 142.

The imaging device 100D is formed in such a manner that the insulatinglayer 212, the transistor 208, the transistor 209, the transistor 210,the light-receiving device 110, the light-emitting device 190, and thelike, which are formed over a formation substrate are transferred ontothe substrate 153. The substrate 153 and the substrate 154 arepreferably flexible. Accordingly, the flexibility of the imaging device100D can be increased.

The inorganic insulating film that can be used as the insulating layer211, the insulating layer 213, and the insulating layer 215 can be usedas the insulating layer 212.

The imaging device 100C shows an example in which the lens 149 is notprovided, and the imaging device 100D shows an example in which the lens149 is provided. The lens 149 can be provided as appropriate inaccordance with usage of a sensor or the like.

[Metal Oxide]

A metal oxide that can be used for the semiconductor layer will bedescribed below.

Note that in this specification and the like, a metal oxide containingnitrogen is also collectively referred to as a metal oxide in somecases. A metal oxide containing nitrogen may be referred to as a metaloxynitride. For example, a metal oxide containing nitrogen, such as zincoxynitride (ZnON), may be used for the semiconductor layer.

Note that in this specification and the like, CAAC (c-axis alignedcrystal) or CAC (Cloud-Aligned Composite) may be stated. Note that CAACrefers to an example of a crystal structure, and CAC refers to anexample of a function or a material composition.

For example, a CAC (Cloud-Aligned Composite)-OS (Oxide Semiconductor)can be used for the semiconductor layer.

A CAC-OS has a conducting function in part of the material and has aninsulating function in another part of the material; as a whole, theCAC-OS has a function of a semiconductor. In the case where the CAC-OSis used in a semiconductor layer of a transistor, the conductingfunction is to allow electrons (or holes) serving as carriers to flow,and the insulating function is to not allow electrons serving ascarriers to flow. By the complementary action of the conducting functionand the insulating function, a switching function (On/Off function) canbe given to the CAC-OS. In the CAC-OS, separation of the functions canmaximize each function.

Furthermore, the CAC-OS includes conductive regions and insulatingregions. The conductive regions have the above-described conductingfunction, and the insulating regions have the above-described insulatingfunction. Furthermore, in some cases, the conductive regions and theinsulating regions in the material are separated at the nanoparticlelevel. Furthermore, in some cases, the conductive regions and theinsulating regions are unevenly distributed in the material.Furthermore, in some cases, the conductive regions are observed to becoupled in a cloud-like manner with their boundaries blurred.

Furthermore, in the CAC-OS, the conductive regions and the insulatingregions each have a size greater than or equal to 0.5 nm and less thanor equal to 10 nm, preferably greater than or equal to 0.5 nm and lessthan or equal to 3 nm, and are dispersed in the material, in some cases.

Furthermore, the CAC-OS includes components having different bandgaps.For example, the CAC-OS includes a component having a wide gap due tothe insulating region and a component having a narrow gap due to theconductive region. In the case of the structure, when carriers flow,carriers mainly flow in the component having a narrow gap. Furthermore,the component having a narrow gap complements the component having awide gap, and carriers also flow in the component having a wide gap inconjunction with the component having a narrow gap. Therefore, in thecase where the above-described CAC-OS is used in a channel formationregion of a transistor, high current driving capability in an on stateof the transistor, that is, a high on-state current and highfield-effect mobility can be obtained.

In other words, the CAC-OS can also be referred to as a matrix compositeor a metal matrix composite.

Oxide semiconductors (metal oxides) are classified into a single crystaloxide semiconductor and a non-single crystal oxide semiconductor.Examples of a non-single-crystal oxide semiconductor include a CAAC-OS(c-axis aligned crystalline oxide semiconductor), a polycrystallineoxide semiconductor, an nc-OS (nanocrystalline oxide semiconductor), anamorphous-like oxide semiconductor (a-like OS), and an amorphous oxidesemiconductor.

The CAAC-OS has c-axis alignment, a plurality of nanocrystals areconnected in the a-b plane direction, and its crystal structure hasdistortion. Note that the distortion refers to a portion where thedirection of a lattice arrangement changes between a region with aregular lattice arrangement and another region with a regular latticearrangement in a region where the plurality of nanocrystals areconnected.

The nanocrystal is basically a hexagon but is not always a regularhexagon and is a non-regular hexagon in some cases. Furthermore, apentagonal or heptagonal lattice arrangement, for example, is includedin the distortion in some cases. Note that it is difficult to observe aclear crystal grain boundary (also referred to as grain boundary) evenin the vicinity of distortion in the CAAC-OS. That is, formation of acrystal grain boundary is found to be inhibited by the distortion of alattice arrangement. This is because the CAAC-OS can tolerate distortionowing to a low density of arrangement of oxygen atoms in the a-b planedirection, an interatomic bond length changed by substitution of a metalelement, and the like.

Furthermore, the CAAC-OS tends to have a layered crystal structure (alsoreferred to as a layered structure) in which a layer containing indiumand oxygen (hereinafter, In layer) and a layer containing the element M,zinc, and oxygen (hereinafter, (M,Zn) layer) are stacked. Note thatindium and the element M can be replaced with each other, and when theelement M in the (M,Zn) layer is replaced with indium, the layer canalso be referred to as an (In,M,Zn) layer. Furthermore, when indium inthe In layer is replaced with the element M, the layer can be referredto as an (In,M) layer.

The CAAC-OS is a metal oxide with high crystallinity. On the other hand,a clear crystal grain boundary cannot be observed in the CAAC-OS; thus,it can be said that a reduction in electron mobility due to the crystalgrain boundary is less likely to occur. Entry of impurities, formationof defects, or the like might decrease the crystallinity of a metaloxide; thus, it can be said that the CAAC-OS is a metal oxide that hassmall amounts of impurities and defects (e.g., oxygen vacancies (alsoreferred to as V_(O))). Thus, a metal oxide including a CAAC-OS isphysically stable. Therefore, the metal oxide including a CAAC-OS isresistant to heat and has high reliability.

In the nc-OS, a microscopic region (e.g., a region with a size greaterthan or equal to 1 nm and less than or equal to 10 nm, in particular, aregion with a size greater than or equal to 1 nm and less than or equalto 3 nm) has a periodic atomic arrangement. Furthermore, there is noregularity of crystal orientation between different nanocrystals in thenc-OS. Thus, the orientation in the whole film is not observed.Accordingly, the nc-OS cannot be distinguished from an a-like OS or anamorphous oxide semiconductor by some analysis methods.

Note that indium-gallium-zinc oxide (hereinafter referred to as IGZO)that is a kind of metal oxide containing indium, gallium, and zinc has astable structure in some cases by being formed of the above-describednanocrystals. In particular, crystals of IGZO tend not to grow in theair and thus, a stable structure is obtained when IGZO is formed ofsmaller crystals (e.g., the above-described nanocrystals) rather thanlarger crystals (here, crystals with a size of several millimeters orseveral centimeters).

An a-like OS is a metal oxide having a structure between those of thenc-OS and an amorphous oxide semiconductor. The a-like OS contains avoid or a low-density region. That is, the a-like OS has lowcrystallinity as compared with the nc-OS and the CAAC-OS.

An oxide semiconductor (metal oxide) can have various structures thatshow different properties. Two or more of the amorphous oxidesemiconductor, the polycrystalline oxide semiconductor, the a-like OS,the nc-OS, and the CAAC-OS may be included in an oxide semiconductor ofone embodiment of the present invention.

A metal oxide film that functions as a semiconductor layer can be formedusing either or both of an inert gas and an oxygen gas. Note that thereis no particular limitation on the flow rate ratio of oxygen (thepartial pressure of oxygen) at the time of forming the metal oxide film.However, to obtain a transistor having high field-effect mobility, theflow rate ratio of oxygen (the partial pressure of oxygen) at the timeof forming the metal oxide film is preferably higher than or equal to 0%and lower than or equal to 30%, further preferably higher than or equalto 5% and lower than or equal to 30%, still further preferably higherthan or equal to 7% and lower than or equal to 15%.

The energy gap of the metal oxide is preferably 2 eV or more, furtherpreferably 2.5 eV or more, still further preferably 2.7 eV or more. Withuse of a metal oxide having such a wide energy gap, the off-statecurrent of the transistor can be reduced.

The substrate temperature during the formation of the metal oxide filmis preferably lower than or equal to 350° C., further preferably higherthan or equal to room temperature and lower than or equal to 200° C.,still further preferably higher than or equal to room temperature andlower than or equal to 130° C. The substrate temperature during thedeposition of the metal oxide film is preferably room temperaturebecause productivity can be increased.

The metal oxide film can be formed by a sputtering method.Alternatively, a PLD method, a PECVD method, a thermal CVD method, anALD method, or a vacuum evaporation method, for example, may be used.

As described above, the imaging device of this embodiment includes alight-receiving device and a light-emitting device in an imaging unit.Thus, the size and weight of an electronic device can be reduced ascompared to the case where a light-emitting device is provided outsidean imaging unit.

In the light-receiving device, at least one of layers other than theactive layer can be common to a layer in the light-emitting device (ELelement). In the light-receiving device, all of the layers other thanthe active layer can be common to the layers in the light-emittingdevice (EL element). For example, with only the addition of the step offorming the active layer to the manufacturing process of thelight-emitting device, the light-emitting device and the light-receivingdevice can be formed over one substrate. In the light-receiving deviceand the light-emitting device, their pixel electrodes can be formedusing the same material in the same step, and their common electrodescan be formed using the same material in the same step. When a circuitelectrically connected to the light-receiving device and a circuitelectrically connected to the light-emitting device are formed using thesame material in the same process, the manufacturing process of theimaging device can be simplified. In such a manner, an imaging devicethat incorporates a light-receiving device and is highly convenient canbe manufactured without complicated steps.

The imaging device of this embodiment includes a coloring layer betweena light-receiving device and a light-emitting device. The colored layermay serve as a bank which electrically isolates the light-receivingdevice from the light-emitting device. Since the colored layer canabsorb stray light in the display device, the sensitivity of a sensorusing a light-receiving device can be increased.

This embodiment can be combined with the other embodiments asappropriate. In this specification, in the case where a plurality ofstructure examples are shown in one embodiment, the structure examplescan be combined as appropriate.

Embodiment 2

In this embodiment, an imaging device of one embodiment of the presentinvention will be described with reference to FIG. 16.

An imaging device of one embodiment of the present invention includesfirst pixel circuits including a light-receiving device and second pixelcircuits including a light-emitting device. The first pixel circuits andthe second pixel circuits are arranged in a matrix.

FIG. 16A illustrates an example of the first pixel circuit including alight-receiving device. FIG. 16B illustrates an example of the secondpixel circuit including a light-emitting device.

A pixel circuit PIX1 illustrated in FIG. 16A includes a light-receivingdevice PD, a transistor M1, a transistor M2, a transistor M3, atransistor M4, and a capacitor C1. Here, an example of the case where aphotodiode is used as the light-receiving device PD is illustrated.

A cathode of the light-receiving device PD is electrically connected toa wiring V1, and an anode is electrically connected to one of a sourceand a drain of the transistor M1. A gate of the transistor M1 iselectrically connected to a wiring TX, and the other of the source andthe drain is electrically connected to one electrode of the capacitorC1, one of a source and a drain of the transistor M2, and a gate of thetransistor M3. A gate of the transistor M2 is electrically connected toa wiring RES, and the other of the source and the drain is electricallyconnected to a wiring V2. One of a source and a drain of the transistorM3 is electrically connected to a wiring V3, and the other of the sourceand the drain is electrically connected to one of a source and a drainof the transistor M4. A gate of the transistor M4 is electricallyconnected to a wiring SE, and the other of the source and the drain iselectrically connected to a wiring OUT1.

A constant potential can be supplied to the wiring V1, the wiring V2,and the wiring V3. When the light-receiving device PD is driven with areverse bias, the wiring V2 can be supplied with a potential lower thanthe potential of the wiring V1. The transistor M2 is controlled by asignal supplied to the wiring RES and has a function of resetting thepotential of a node connected to the gate of the transistor M3 to apotential supplied to the wiring V2. The transistor M1 is controlled bya signal supplied to the wiring TX and has a function of controlling thetiming at which the potential of the node changes, in accordance with acurrent flowing through the light-receiving device PD. The transistor M3functions as an amplifier transistor for performing output in responseto the potential of the node. The transistor M4 is controlled by asignal supplied to the wiring SE and functions as a selection transistorfor reading an output corresponding to the potential of the node by anexternal circuit connected to the wiring OUT1. Note that the connectionrelationship between the cathode and the anode of the light-receivingdevice PD in FIG. 16A may be reversed.

A pixel circuit PIX2 illustrated in FIG. 16B includes a light-emittingdevice EL, a transistor M5, a transistor M6, a transistor M7, and acapacitor C2. Here, an example in which a light-emitting diode is usedas the light-emitting device EL is illustrated. In particular, anorganic EL element is preferably used as the light-emitting device EL.

A gate of the transistor M5 is electrically connected to a wiring VG,one of a source and a drain is electrically connected to a wiring VS,and the other of the source and the drain is electrically connected toone electrode of the capacitor C2 and a gate of the transistor M6. Oneof a source and a drain of the transistor M6 is electrically connectedto a wiring V4, and the other of the source and the drain iselectrically connected to an anode of the light-emitting device EL andone of a source and a drain of the transistor M7. A gate of thetransistor M7 is electrically connected to a wiring M5, and the other ofthe source and the drain is electrically connected to a wiring OUT2. Acathode of the light-emitting device EL is electrically connected to awiring V5.

A constant potential is supplied to the wiring V4 and the wiring V5. Inthe light-emitting device EL, the anode side can have a high potentialand the cathode side can have a lower potential than the anode side. Thetransistor M5 is controlled by a signal supplied to the wiring VG andfunctions as a selection transistor for controlling a selection state ofthe pixel circuit PIX2. The transistor M6 functions as a drivingtransistor that controls a current flowing through the light-emittingdevice EL in accordance with a potential supplied to the gate. When thetransistor M5 is in an on state, a potential supplied to the wiring VSis supplied to the gate of the transistor M6, and the emission luminanceof the light-emitting device EL can be controlled in accordance with thepotential. The transistor M7 is controlled by a signal supplied to thewiring MS and has a function of outputting a potential between thetransistor M6 and the light-emitting device EL to the outside throughthe wiring OUT2.

The wiring V1, to which the cathode of the light-receiving device PD iselectrically connected, and the wiring V5, to which the cathode of thelight-emitting device EL is electrically connected, can be provided inthe same layer and have the same level of potential.

Note that in the imaging device of this embodiment, the light-emittingdevice may be made to emit light in a pulsed manner so as to display animage. A reduction in the driving time of the light-emitting device canreduce power consumption of the display device and suppress heatgeneration of the display device. An organic EL element is particularlypreferable because of its favorable frequency characteristics. Thefrequency can be higher than or equal to 1 kHz and lower than or equalto 100 MHz, for example.

Here, a transistor in which a metal oxide (an oxide semiconductor) isused in a semiconductor layer where a channel is formed is preferablyused as the transistor M1, the transistor M2, the transistor M3, and thetransistor M4 included in the pixel circuit PIX1 and the transistor M5,the transistor M6, and the transistor M7 included in the pixel circuitPIX2.

A transistor using a metal oxide having a wider band gap and a lowercarrier density than silicon can achieve an extremely low off-statecurrent. Thus, such a low off-state current enables retention of chargesaccumulated in a capacitor that is connected in series with thetransistor for a long time. Therefore, it is particularly preferable touse a transistor using an oxide semiconductor as the transistor M1, thetransistor M2, and the transistor M5 each of which is connected inseries with the capacitor C1 or the capacitor C2. Moreover, the use oftransistors using an oxide semiconductor as the other transistors canreduce the manufacturing cost.

Alternatively, transistors using silicon as a semiconductor in which achannel is formed can be used as the transistor M1 to the transistor M7.In particular, the use of silicon with high crystallinity, such assingle crystal silicon or polycrystalline silicon, is preferable becausehigh field-effect mobility is achieved and higher-speed operation ispossible.

Alternatively, a transistor using an oxide semiconductor may be used asone or more of the transistor M1 to the transistor M7, and transistorsusing silicon may be used as the other transistors.

Although n-channel transistors are shown as the transistors in FIG. 16Aand FIG. 16B, p-channel transistors can be used as appropriate.

The transistors included in the pixel circuit PIX1 and the transistorsincluded in the pixel circuit PIX2 are preferably formed side by sideover the same substrate. It is particularly preferable that thetransistors included in the pixel circuits PIX1 and the transistorsincluded in the pixel circuits PIX2 be periodically arranged in oneregion.

One or more layers including the transistor and/or the capacitor arepreferably provided to overlap with the light-receiving device PD or thelight-emitting device EL. Thus, the effective area of each pixel circuitcan be reduced, and a high-definition imaging unit can be achieved.

This embodiment can be combined with the other embodiments asappropriate.

Embodiment 3

In this embodiment, electronic devices of one embodiment of the presentinvention will be described with reference to FIG. 17 to FIG. 19.

An electronic device in this embodiment is provided with the imagingdevice of one embodiment of the present invention. For example, theimaging device of one embodiment of the present invention can be used ina display portion of the electronic device. The imaging device of oneembodiment of the present invention has a function of sensing light, andthus can perform biological authentication with the display portion ordetect a touch or a near touch on the display portion. Thus, theelectronic device can have improved functionality and convenience, forexample.

Examples of the electronic devices include a digital camera, a digitalvideo camera, a digital photo frame, a mobile phone, a portable gameconsole, a portable information terminal, and an audio reproducingdevice, in addition to electronic devices with a relatively largescreen, such as a television device, a desktop or laptop personalcomputer, a monitor of a computer or the like, digital signage, and alarge game machine such as a pachinko machine.

The electronic device in this embodiment may include a sensor (a sensorhaving a function of measuring force, displacement, position, speed,acceleration, angular velocity, rotational frequency, distance, light,liquid, magnetism, temperature, a chemical substance, sound, time,hardness, electric field, current, voltage, electric power, radiation,flow rate, humidity, gradient, oscillation, a smell, or infrared rays).

The electronic device in this embodiment can have a variety offunctions. For example, the electronic device can have a function ofdisplaying a variety of data (a still image, a moving image, a textimage, and the like) on the display portion, a touch panel function, afunction of displaying a calendar, date, time, and the like, a functionof executing a variety of software (programs), a wireless communicationfunction, and a function of reading out a program or data stored in arecording medium.

An electronic device 6500 illustrated in FIG. 17A is a portableinformation terminal that can be used as a smartphone.

The electronic device 6500 includes a housing 6501, a display portion6502, a power button 6503, operation buttons 6504, a speaker 6505, amicrophone 6506, a camera 6507, a light source 6508, and the like. Thedisplay portion 6502 has a touch panel function.

The imaging device of one embodiment of the present invention can beused in the display portion 6502.

FIG. 17B is a schematic cross-sectional view including an end portion ofthe housing 6501 on the microphone 6506 side.

A protection member 6510 having a light-transmitting property isprovided on a display surface side of the housing 6501, and a displaypanel 6511, an optical member 6512, a touch sensor panel 6513, a printedcircuit board 6517, a battery 6518, and the like are provided in a spacesurrounded by the housing 6501 and the protection member 6510.

The display panel 6511, the optical member 6512, and the touch sensorpanel 6513 are fixed to the protection member 6510 with an adhesivelayer (not shown).

Part of the display panel 6511 is folded back in a region outside thedisplay portion 6502, and an FPC 6515 is connected to the part that isfolded back. An IC 6516 is mounted on the FPC 6515. The FPC 6515 isconnected to a terminal provided on the printed circuit board 6517.

A flexible display of one embodiment of the present invention can beused as the display panel 6511. Thus, an extremely lightweightelectronic device can be provided. Since the display panel 6511 isextremely thin, the battery 6518 with high capacity can be mounted withthe thickness of the electronic device controlled. An electronic devicewith a narrow frame can be obtained when part of the display panel 6511is folded back so that the portion connected to the FPC 6515 ispositioned on the rear side of a pixel portion.

FIG. 18A illustrates an example of a television device. In a televisiondevice 7100, a display portion 7000 is incorporated in a housing 7101.Here, a structure in which the housing 7101 is supported by a stand 7103is illustrated.

The imaging device of one embodiment of the present invention can beused in the display portion 7000.

Operation of the television device 7100 illustrated in FIG. 18A can beperformed with an operation switch provided in the housing 7101 or aseparate remote controller 7111. Alternatively, the display portion 7000may include a touch sensor, and the television device 7100 may beoperated by touch on the display portion 7000 with a finger or the like.The remote controller 7111 may be provided with a display portion fordisplaying data output from the remote controller 7111. With operationkeys or a touch panel provided in the remote controller 7111, channelsand volume can be operated and videos displayed on the display portion7000 can be operated.

Note that the television device 7100 has a structure in which areceiver, a modem, and the like are provided. A general televisionbroadcast can be received with the receiver. When the television deviceis connected to a communication network with or without wires via themodem, one-way (from a transmitter to a receiver) or two-way (between atransmitter and a receiver or between receivers, for example) datacommunication can be performed.

FIG. 18B illustrates an example of a laptop personal computer. A laptoppersonal computer 7200 includes a housing 7211, a keyboard 7212, apointing device 7213, an external connection port 7214, and the like. Inthe housing 7211, the display portion 7000 is incorporated.

The imaging device of one embodiment of the present invention can beused in the display portion 7000.

FIG. 18C and FIG. 18D illustrate examples of digital signage.

Digital signage 7300 illustrated in FIG. 18C includes a housing 7301,the display portion 7000, a speaker 7303, and the like. Furthermore, thedigital signage can include an LED lamp, operation keys (including apower switch or an operation switch), a connection terminal, a varietyof sensors, a microphone, and the like.

FIG. 18D is digital signage 7400 attached to a cylindrical pillar 7401.The digital signage 7400 includes the display portion 7000 providedalong a curved surface of the pillar 7401.

The imaging device of one embodiment of the present invention can beused for the display portion 7000 in FIG. 18C and FIG. 18D.

A larger area of the display portion 7000 can increase the amount ofdata that can be provided at a time. The larger display portion 7000attracts more attention, so that the effectiveness of the advertisementcan be increased, for example.

The use of a touch panel in the display portion 7000 is preferablebecause in addition to display of a still image or a moving image on thedisplay portion 7000, intuitive operation by a user is possible.Moreover, for an application for providing information such as routeinformation or traffic information, usability can be enhanced byintuitive operation.

As illustrated in FIG. 18C and FIG. 18D, it is preferable that thedigital signage 7300 or the digital signage 7400 can work with aninformation terminal 7311 or an information terminal 7411 such as asmartphone a user has through wireless communication. For example,information of an advertisement displayed on the display portion 7000can be displayed on a screen of the information terminal 7311 or theinformation terminal 7411. By operation of the information terminal 7311or the information terminal 7411, display on the display portion 7000can be switched.

It is possible to make the digital signage 7300 or the digital signage7400 execute a game with use of the screen of the information terminal7311 or the information terminal 7411 as an operation means(controller). Thus, an unspecified number of users can join in and enjoythe game concurrently.

Electronic devices shown in FIG. 19A to FIG. 19F include a housing 9000,a display portion 9001, a speaker 9003, an operation key 9005 (includinga power switch or an operation switch), a connection terminal 9006, asensor 9007 (a sensor having a function of measuring force,displacement, position, speed, acceleration, angular velocity,rotational frequency, distance, light, liquid, magnetism, temperature, achemical substance, sound, time, hardness, electric field, current,voltage, electric power, radiation, flow rate, humidity, gradient,oscillation, a smell, or infrared rays), a microphone 9008, and thelike.

The electronic devices shown in FIG. 19A to FIG. 19F have a variety offunctions. For example, the electronic devices can have a function ofdisplaying a variety of data (a still image, a moving image, a textimage, and the like) on the display portion, a touch panel function, afunction of displaying a calendar, date, time, and the like, a functionof controlling processing with use of a variety of software (programs),a wireless communication function, and a function of reading out andprocessing a program or data stored in a recording medium. Note that thefunctions of the electronic devices are not limited thereto, and theelectronic devices can have a variety of functions. The electronicdevices may include a plurality of display portions. The electronicdevices may each include a camera or the like and have a function oftaking a still image or a moving image and storing the taken image in arecording medium (an external recording medium or a recording mediumincorporated in the camera), a function of displaying the taken image onthe display portion, or the like.

The details of the electronic devices illustrated in FIG. 19A to FIG.19F are described below.

FIG. 19A is a perspective view showing a portable information terminal9101. For example, the portable information terminal 9101 can be used asa smartphone. Note that the portable information terminal 9101 may beprovided with the speaker 9003, the connection terminal 9006, the sensor9007, or the like. The portable information terminal 9101 can displaycharacters and image information on its plurality of surfaces. FIG. 19Ashows an example where three icons 9050 are displayed. Information 9051indicated by dashed rectangles can be displayed on another surface ofthe display portion 9001. Examples of the information 9051 includenotification of reception of an e-mail, SNS, or an incoming call, thetitle and sender of an e-mail, SNS, or the like, the date, the time,remaining battery, and the reception strength of an antenna.Alternatively, the icon 9050 or the like may be displayed in theposition where the information 9051 is displayed.

FIG. 19B is a perspective view showing a portable information terminal9102. The portable information terminal 9102 has a function ofdisplaying information on three or more surfaces of the display portion9001. Here, an example in which information 9052, information 9053, andinformation 9054 are displayed on different surfaces is shown. Forexample, a user can check the information 9053 displayed in a positionthat can be observed from above the portable information terminal 9102,with the portable information terminal 9102 put in a breast pocket ofhis/her clothes. The user can see the display without taking out theportable information terminal 9102 from the pocket and decide whether toanswer the call, for example.

FIG. 19C is a perspective view showing a watch-type portable informationterminal 9200. For example, the portable information terminal 9200 canbe used as a smart watch. The display surface of the display portion9001 is curved and provided, and display can be performed along thecurved display surface. Mutual communication between the portableinformation terminal 9200 and, for example, a headset capable ofwireless communication enables hands-free calling. With the connectionterminal 9006, the portable information terminal 9200 can perform mutualdata transmission with another information terminal and charging. Notethat the charging operation may be performed by wireless power feeding.

FIG. 19D, FIG. 19E, and FIG. 19F are perspective views showing afoldable portable information terminal 9201. FIG. 19D is a perspectiveview of an opened state of the portable information terminal 9201, FIG.19F is a perspective view of a folded state thereof, and FIG. 19E is aperspective view of a state in the middle of change from one of FIG. 19Dand FIG. 19F to the other. The portable information terminal 9201 ishighly portable in the folded state and is highly browsable in theopened state because of a seamless large display region. The displayportion 9001 of the portable information terminal 9201 is supported bythree housings 9000 joined by hinges 9055. For example, the displayportion 9001 can be folded with a radius of curvature greater than orequal to 0.1 mm and less than or equal to 150 mm.

This embodiment can be combined with the other embodiments asappropriate.

REFERENCE NUMERALS

BM: light-blocking layer, EL: light-emitting device, PD: light-receivingdevice, 10A: imaging device, 10B: imaging device, 10C: imaging device,10D: imaging device, 10E: imaging device, 10F: imaging device, 10G:imaging device, 10H: imaging device, 10J: imaging device, 10K: imagingdevice, 10L: imaging device, 10M: imaging device, 10: imaging device,21: light-emitting, 22: light, 23 a: light, 23 b: reflected light, 23 c:light, 23 d: reflected light, 41: transistor, 42: transistor, 51:substrate, 52: subject, 53: layer, 55: layer, 57: layer, 59: substrate,60B: subpixel, 60G: subpixel, 60PD: subpixel, 60R: subpixel, 60W:subpixel, 60: pixel, 61: imaging unit, 62: driver circuit portion, 63:driver circuit portion, 64: driver circuit portion, 65: circuit portion,71: arithmetic circuit, 73: memory, 82: wiring, 83: wiring, 84: wiring,85: wiring, 86: wiring, 87: wiring, 91B: light-emitting device, 91G:light-emitting device, 91PD: light-receiving device, 91R: light-emittingdevice, 91W: light-emitting device, 100A: imaging device, 100B: imagingdevice, 100C: imaging device, 100D: imaging device, 110: light-receivingdevice, 111: pixel electrode, 112: common layer, 113: active layer, 114:common layer, 115: common electrode, 142: adhesive layer, 143: space,146: lens array, 147: coloring layer, 148 a: coloring layer, 148 b:coloring layer, 148 c: coloring layer, 148: coloring layer, 149: lens,151: substrate, 152: substrate, 153: substrate, 154: substrate, 155:adhesive layer, 162: imaging unit, 164: circuit, 165: wiring, 166:conductive layer, 172: FPC, 173: IC, 182: buffer layer, 184: bufferlayer, 190: light-emitting device, 191: pixel electrode, 192: bufferlayer, 193: light-emitting layer, 194: buffer layer, 195 a: inorganicinsulating layer, 195 b: organic insulating layer, 195 c: inorganicinsulating layer, 195: protective layer, 201: transistor, 202:transistor, 204: connection portion, 205: transistor, 206: transistor,208: transistor, 209: transistor, 210: transistor, 211: insulatinglayer, 212: insulating layer, 213: insulating layer, 214: insulatinglayer, 215: insulating layer, 216: bank, 217: bank, 218: insulatinglayer, 221: conductive layer, 222 a: conductive layer, 222 b: conductivelayer, 223: conductive layer, 225: insulating layer, 228: region, 231 i:channel formation region, 231 n: low-resistance region, 231:semiconductor layer, 242: connection layer, 6500: electronic device,6501: housing, 6502: display portion, 6503: power button, 6504:operation button, 6505: speaker, 6506: microphone, 6507: camera, 6508:light source, 6510: protection member, 6511: display panel, 6512:optical member, 6513: touch sensor panel, 6515: FPC, 6516: IC, 6517:printed circuit board, 6518: battery, 7000: display portion, 7100:television, 7101: housing, 7103: stand, 7111: remote controller, 7200:laptop, 7211: housing, 7212: keyboard, 7213: pointing device, 7214:external connection port, 7300: digital signage, 7301: housing, 7303:speaker, 7311: information terminal, 7400: digital signage, 7401:pillar, 7411: information terminal, 9000: housing, 9001: displayportion, 9003: speaker, 9005: control key, 9006: connection terminal,9007: sensor, 9008: microphone, 9050: icon, 9051: information, 9052:information, 9053: information, 9054: information, 9055: hinge, 9101:portable information terminal, 9102: portable information terminal,9200: portable information terminal, 9201: portable information terminal

1. An imaging device comprising: an imaging unit; a memory; and anarithmetic circuit, wherein the imaging unit comprises a light-receivingdevice, a first light-emitting device, and a second light-emittingdevice, wherein the first light-emitting device is configured to emitlight in a wavelength range that is different from a wavelength range oflight emitted by the second light-emitting device, wherein the imagingunit is configured to make the first light-emitting device emit lightand acquire first image data, wherein the imaging unit is configured tomake the second light-emitting device emit light and acquire secondimage data, wherein the memory is configured to retain first referencedata and second reference data, wherein the arithmetic circuit isconfigured to correct the first image data with the use of the firstreference data retained in the memory and calculate first correctionimage data, wherein the arithmetic circuit is configured to correct thesecond image data with the use of the second reference data retained inthe memory and calculate second correction image data, wherein thearithmetic circuit is configured to combine the first correction imagedata and the second correction image data to generate synthesized imagedata, wherein the light-receiving device comprises a first pixelelectrode, and wherein the first light-emitting device comprises asecond pixel electrode on the same plane as the first pixel electrode.2. The imaging device according to claim 1, wherein the light-receivingdevice comprises an active layer and a common electrode, wherein thefirst light-emitting device comprises a light-emitting layer and thecommon electrode, wherein the active layer is over the first pixelelectrode, wherein the active layer comprises a first organic compound,wherein the light-emitting layer is over the second pixel electrode,wherein the light-emitting layer comprises a second organic compound,and wherein the common electrode comprises a portion overlapping withthe first pixel electrode with the active layer therebetween and aportion overlapping with the second pixel electrode with thelight-emitting layer therebetween.
 3. The imaging device according toclaim 1, wherein the imaging unit comprises a lens, wherein the lenscomprises a portion overlapping with the light-receiving device, whereinthe lens is over the first pixel electrode, and wherein light passingthrough the lens enters the light-receiving device.
 4. An imaging modulecomprises: the imaging device according to claim 1; and at least any oneor more of a connector and an integrated circuit.
 5. An electronicdevice comprises: the imaging module according to claim 4; and at leastany one or more of an antenna, a battery, a housing, a camera, aspeaker, a microphone, and an operation button.
 6. An imaging methodcomprising: the step of making a first light-emitting device emit lightand acquiring first image data; the step of correcting the first imagedata with the use of first reference data and calculating firstcorrection image data; the step of making a second light-emitting deviceemit light and acquiring second image data; the step of correcting thesecond image data with the use of second reference data and calculatingsecond correction image data; and the step of combining the firstcorrection image data and the second correction image data andgenerating synthesized image data, wherein the first light-emittingdevice is configured to emit light in a wavelength range that isdifferent from a wavelength range of light emitted by the secondlight-emitting device.